Tuesday, February 11, 2014

What Is a Black Hole?

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

How Big Are Black Holes?

Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter, or "stuff," in an object.

Another kind of black hole is called "stellar." Its mass can be up to 20 times more than the mass of the sun. There may be many, many stellar mass black holes in Earth's galaxy. Earth's galaxy is called the Milky Way.

The largest black holes are called "supermassive." These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.

How Do Black Holes Form?

Scientists think the smallest black holes formed when the universe began.

Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.

Scientists think supermassive black holes were made at the same time as the galaxy they are in.

If Black Holes Are "Black," How Do Scientists Know They Are There?

A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole. Scientists can study stars to find out if they are flying around, or orbiting, a black hole.

When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.

Could a Black Hole Destroy Earth?

Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.

Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in. The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now.

The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.

Does light have mass?

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Does light have mass?

The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes".

Light is composed of photons, so we could ask if the photon has mass. The answer is then definitely "no": the photon is a massless particle. According to theory it has energy and momentum but no mass, and this is confirmed by experiment to within strict limits. Even before it was known that light is composed of photons, it was known that light carries momentum and will exert pressure on a surface. This is not evidence that it has mass since momentum can exist without mass.

Sometimes people like to say that the photon does have mass because a photon has energy E = hf where h is Planck's constant and f is the frequency of the photon. Energy, they say, is equivalent to mass according to Einstein's famous formula E = mc². They also say that a photon has momentum, and momentum p is related to mass m by p = mv. What they are talking about is "relativistic mass", an old concept that can cause confusion. Relativistic mass is a measure of the energy E of a particle, which changes with velocity. By convention, relativistic mass is not usually called the mass of a particle in contemporary physics so, at least semantically, it is wrong to say the photon has mass in this way. But you can say that the photon has relativistic mass if you really want to. In modern terminology the mass of an object is its invariant mass, which is zero for a photon.

If we now return to the question "Does light have mass?", this can be taken to mean different things if the light is moving freely or trapped in a container. The definition of the invariant mass of an object is m = sqrt{E²/c⁴ - p²/c²}. By this definition a beam of light is massless like the photons it is composed of. However, if light is trapped in a box with perfect mirrors so the photons are continually reflected back and forth in both directions symmetrically in the box, then the total momentum is zero in the box's frame of reference but the energy is not. Therefore the light adds a small contribution to the mass of the box. This could be measured--in principle at least--either by the greater force required to accelerate the box, or by an increase in its gravitational pull. You might say that the light in the box has mass, but it would be more correct to say that the light contributes to the total mass of the box of light. You should not use this to justify the statement that light has mass in general.

Part of this discussion is only concerned with semantics. It might be thought that it would be better to regard the mass of the photons to be their (nonzero) relativistic mass, as opposed to their (zero) invariant mass. We could then consistently talk about the light having mass independently of whether or not it is contained. If relativistic mass is used for all objects, then mass is conserved and the mass of an object is the sum of the masses of its parts. However, modern usage defines mass as the invariant mass of an object mainly because the invariant mass is more useful when doing any kind of calculation. In this case mass is not conserved and the mass of an object is not the sum of the masses of its parts. Thus, the mass of a box of light is more than the mass of the box and the sum of the masses of the photons (the latter being zero). Relativistic mass is equivalent to energy, which is why relativistic mass is not a commonly used term nowadays. In the modern view "mass" is not equivalent to energy; mass is just that part of the energy of a body which is not kinetic energy. Mass is independent of velocity whereas energy is not.

Let's try to phrase this another way. What is the meaning of the equation E=mc²? You can interpret it to mean that energy is the same thing as mass except for a conversion factor equal to the square of the speed of light. Then wherever there is mass there is energy and wherever there is energy there is mass. In that case photons have mass, but we call it relativistic mass. Another way to use Einstein's equation would be to keep mass and energy as separate and use it as an equation which applies when mass is converted to energy or energy is converted to mass--usually in nuclear reactions. The mass is then independent of velocity and is closer to the old Newtonian concept. In that case, only the total of energy and mass would be conserved, but it seems better to try to keep the conservation of energy. The interpretation most widely used is a compromise in which mass is invariant and always has energy so that total energy is conserved but kinetic energy and radiation does not have mass. The distinction is purely a matter of semantic convention.

Sometimes people ask "If light has no mass how can it be deflected by the gravity of a star?". One answer is that all particles, including photons, move along geodesics in general relativity and the path they follow is independent of their mass. The deflection of starlight by the sun was first measured by Arthur Eddington in 1919. The result was consistent with the predictions of general relativity and inconsistent with the newtonian theory. Another answer is that the light has energy and momentum which couples to gravity. The energy-momentum 4-vector of a particle, rather than its mass, is the gravitational analogue of electric charge. (The corresponding analogue of electric current is the energy-momentum stress tensor which appears in the gravitational field equations of general relativity.) A massless particle can have energy E and momentum p because mass is related to these by the equation m² = E²/c⁴ - p²/c², which is zero for a photon because E = pc for massless radiation. The energy and momentum of light also generates curvature of spacetime, so general relativity predicts that light will attract objects gravitationally. This effect is far too weak to have yet been measured. The gravitational effect of photons does not have any cosmological effects either (except perhaps in the first instant after the Big Bang). And there seem to be far too few with too little energy to make any noticeable contribution to dark matter.

Why is the sky blue?

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Why is the sky blue?

A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scattered out and away from the line of sight.

The white light from the sun is a mixture of all colours of the rainbow. This was demonstrated by Isaac Newton, who used a prism to separate the different colours and so form a spectrum. The colours of light are distinguished by their different wavelengths. The visible part of the spectrum ranges from red light with a wavelength of about 720 nm, to violet with a wavelength of about 380 nm, with orange, yellow, green, blue and indigo between. The three different types of colour receptors in the retina of the human eye respond most strongly to red, green and blue wavelengths, giving us our colour vision.

Tyndall Effect

The first steps towards correctly explaining the colour of the sky were taken by John Tyndall in 1859. He discovered that when light passes through a clear fluid holding small particles in suspension, the shorter blue wavelengths are scattered more strongly than the red. This can be demonstrated by shining a beam of white light through a tank of water with a little milk or soap mixed in. From the side, the beam can be seen by the blue light it scatters; but the light seen directly from the end is reddened after it has passed through the tank. The scattered light can also be shown to be polarised using a filter of polarised light, just as the sky appears a deeper blue through polaroid sun glasses.
This is most correctly called the Tyndall effect, but it is more commonly known to physicists as Rayleigh scattering—after Lord Rayleigh, who studied it in more detail a few years later. He showed that the amount of light scattered is inversely proportional to the fourth power of wavelength for sufficiently small particles. It follows that blue light is scattered more than red light by a factor of (700/400)⁴ ~= 10.

Dust or Molecules?

Tyndall and Rayleigh thought that the blue colour of the sky must be due to small particles of dust and droplets of water vapour in the atmosphere. Even today, people sometimes incorrectly say that this is the case. Later scientists realised that if this were true, there would be more variation of sky colour with humidity or haze conditions than was actually observed, so they supposed correctly that the molecules of oxygen and nitrogen in the air are sufficient to account for the scattering. The case was finally settled by Einstein in 1911, who calculated the detailed formula for the scattering of light from molecules; and this was found to be in agreement with experiment. He was even able to use the calculation as a further verification of Avogadro's number when compared with observation. The molecules are able to scatter light because the electromagnetic field of the light waves induces electric dipole moments in the molecules.

Why not violet?

If shorter wavelengths are scattered most strongly, then there is a puzzle as to why the sky does not appear violet, the colour with the shortest visible wavelength. The spectrum of light emission from the sun is not constant at all wavelengths, and additionally is absorbed by the high atmosphere, so there is less violet in the light. Our eyes are also less sensitive to violet. That's part of the answer; yet a rainbow shows that there remains a significant amount of visible light coloured indigo and violet beyond the blue. The rest of the answer to this puzzle lies in the way our vision works. We have three types of colour receptors, or cones, in our retina. They are called red, blue and green because they respond most strongly to light at those wavelengths. As they are stimulated in different proportions, our visual system constructs the colours we see.

Response curves for the three types of cone in the human eye

When we look up at the sky, the red cones respond to the small amount of scattered red light, but also less strongly to orange and yellow wavelengths. The green cones respond to yellow and the more strongly scattered green and green-blue wavelengths. The blue cones are stimulated by colours near blue wavelengths, which are very strongly scattered. If there were no indigo and violet in the spectrum, the sky would appear blue with a slight green tinge. However, the most strongly scattered indigo and violet wavelengths stimulate the red cones slightly as well as the blue, which is why these colours appear blue with an added red tinge. The net effect is that the red and green cones are stimulated about equally by the light from the sky, while the blue is stimulated more strongly. This combination accounts for the pale sky blue colour. It may not be a coincidence that our vision is adjusted to see the sky as a pure hue. We have evolved to fit in with our environment; and the ability to separate natural colours most clearly is probably a survival advantage.

A multicoloured sunset over the Firth of Forth in Scotland.

Sunsets

When the air is clear the sunset will appear yellow, because the light from the sun has passed a long distance through air and some of the blue light has been scattered away. If the air is polluted with small particles, natural or otherwise, the sunset will be more red. Sunsets over the sea may also be orange, due to salt particles in the air, which are effective Tyndall scatterers. The sky around the sun is seen reddened, as well as the light coming directly from the sun. This is because all light is scattered relatively well through small angles—but blue light is then more likely to be scattered twice or more over the greater distances, leaving the yellow, red and orange colours.

A blue haze over the mountains of Les Vosges in France.

Blue Haze and Blue Moon

Clouds and dust haze appear white because they consist of particles larger than the wavelengths of light, which scatter all wavelengths equally (Mie scattering). But sometimes there might be other particles in the air that are much smaller. Some mountainous regions are famous for their blue haze. Aerosols of terpenes from the vegetation react with ozone in the atmosphere to form small particles about 200 nm across, and these particles scatter the blue light. A forest fire or volcanic eruption may occasionally fill the atmosphere with fine particles of 500—800 nm across, being the right size to scatter red light. This gives the opposite to the usual Tyndall effect, and may cause the moon to have a blue tinge since the red light has been scattered out. This is a very rare phenomenon, occurring literally once in a blue moon.

Opalescence

The Tyndall effect is responsible for some other blue coloration's in nature: such as blue eyes, the opalescence of some gem stones, and the colour in the blue jay's wing. The colours can vary according to the size of the scattering particles. When a fluid is near its critical temperature and pressure, tiny density fluctuations are responsible for a blue coloration known as critical opalescence. People have also copied these natural effects by making ornamental glasses impregnated with particles, to give the glass a blue sheen. But not all blue colouring in nature is caused by scattering. Light under the sea is blue because water absorbs longer wavelength of light through distances over about 20 metres. When viewed from the beach, the sea is also blue because it reflects the sky, of course. Some birds and butterflies get their blue colorations by diffraction effects.

Why is the Mars sky red?

Images sent back from the Viking Mars landers in 1977 and from Pathfinder in 1997 showed a red sky seen from the Martian surface. This was due to red iron-rich dusts thrown up in the dust storms occurring from time to time on Mars. The colour of the Mars sky will change according to weather conditions. It should be blue when there have been no recent storms, but it will be darker than the earth's daytime sky because of Mars' thinner atmosphere.

Dark Energy, Dark Matter

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Dark Energy, Dark Matter

In the early 1990's, one thing was fairly certain about the expansion of the Universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the Universe had to slow. The Universe is full of matter and the attractive force of gravity pulls all matter together. Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the Universe was actually expanding more slowly than it is today. So the expansion of the Universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it.
Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.

What Is Dark Energy?

Universe Dark Energy-1 Expanding Universe

This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago, when objects in the universe began flying apart as a faster rate. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart.

NASA/STSci/Ann Feild

More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn't be called "normal" matter at all, since it is such a small fraction of the Universe.
One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the Universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the Universe.

Dark Matter Core Defies Explanation

This image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520. The result could present a challenge to basic theories of dark matter.

Another explanation for how space acquires energy comes from the quantum theory of matter. In this theory, "empty space" is actually full of temporary ("virtual") particles that continually form and then disappear. But when physicists tried to calculate how much energy this would give empty space, the answer came out wrong - wrong by a lot. The number came out 10¹²⁰ times too big. That's a 1 with 120 zeros after it. It's hard to get an answer that bad. So the mystery continues.
Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field, something that fills all of space but something whose effect on the expansion of the Universe is the opposite of that of matter and normal energy. Some theorists have named this "quintessence," after the fifth element of the Greek philosophers. But, if quintessence is the answer, we still don't know what it is like, what it interacts with, or why it exists. So the mystery continues.
A last possibility is that Einstein's theory of gravity is not correct. That would not only affect the expansion of the Universe, but it would also affect the way that normal matter in galaxies and clusters of galaxies behaved. This fact would provide a way to decide if the solution to the dark energy problem is a new gravity theory or not: we could observe how galaxies come together in clusters. But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein's theory is known to do, and still give us the different prediction for the Universe that we need? There are candidate theories, but none are compelling. So the mystery continues.
The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data.

What Is Dark Matter?

Abell 2744: Pandora's Cluster Revealed

One of the most complicated and dramatic collisions between galaxy clusters ever seen is captured in this new composite image of Abell 2744. The blue shows a map of the total mass concentration (mostly dark matter).

By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?
We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.
However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles).

Look at this series: 58, 52, 46, 40, 34, ... What number should come next?

123 6:06 AM Math No comments

Look at this series: 58, 52, 46, 40, 34, ... What number should come next?

A 26 B 28
C 30 D 32

Math Magic/Tricks

123 10:50 PM Math No comments

Math Magic/Tricks

Trick 1: Number below 10
Step1: Think of a number below 10.
Step2: Double the number you have thought.
Step3: Add 6 with the getting result.
Step4: Half the answer, that is divide it by 2.
Step5: Take away the number you have thought from the answer, that is, subtract the answer from the number you have thought.

Answer: 3

Trick 2: Any Number
Step1: Think of any number.
Step2: Subtract the number you have thought with 1.
Step3: Multiply the result with 3.
Step4: Add 12 with the result.
Step5: Divide the answer by 3.
Step6: Add 5 with the answer.
Step7: Take away the number you have thought from the answer, that is, subtract the answer from the number you have thought.

Answer: 8

Trick 3: Any Number
Step1: Think of any number.
Step2: Multiply the number you have thought with 3.
Step3: Add 45 with the result.
Step4: Double the result.
Step5: Divide the answer by 6.
Step6: Take away the number you have thought from the answer, that is, subtract the answer from the number you have thought.

Answer: 15

Trick 4: Same 3 Digit Number
Step1: Think of any 3 digit number, but each of the digits must be the same as. Ex: 333, 666.
Step2: Add up the digits.
Step3: Divide the 3 digit number with the digits added up.

Answer: 37

Trick 5: 2 Single Digit Numbers
Step1: Think of 2 single digit numbers.
Step2: Take any one of the number among them and double it.
Step3: Add 5 with the result.
Step4: Multiply the result with 5.
Step5: Add the second number to the answer.
Step6: Subtract the answer with 4.
Step7: Subtract the answer again with 21.

Answer: 2 Single Digit Numbers.

Trick 6: 1, 2, 4, 5, 7, 8
Step1: Choose a number from 1 to 6.
Step2: Multiply the number with 9.
Step3: Multiply the result with 111.
Step4: Multiply the result by 1001.
Step5: Divide the answer by 7.

Answer: All the above numbers will be present.

Trick 7: 1089
Step1: Think of a 3 digit number.
Step2: Arrange the number in descending order.
Step3: Reverse the number and subtract it with the result.
Step4: Remember it and reverse the answer mentally.
Step5: Add it with the result, you have got.

Answer: 1089

Trick 8: x7x11x13
Step1: Think of a 3 digit number.
Step2: Multiply it with x7x11x13.

Ex: Number: 456, Answer: 456456

Trick 9: x3x7x13x37
Step1: Think of a 2 digit number.
Step2: Multiply it with x3x7x13x37.

Ex: Number: 45, Answer: 454545

Trick 10: 9091
Step1:Think of a 5 digit number.
Step2:Multiply it with 11.
Step3:Multiply it with 9091.

Ex: Number: 12345,Answer:1234512345

Math

123 10:41 PM Math No comments

Questions 1:

If Log_x (1 / 8) = - 3 / 2, then x is equal to

A. - 4
B. 4
C. 1 / 4
D. 10
Question 2:

20 % of 2 is equal to

A. 20
B. 4
C. 0.4
D. 0.04
Questions 3:

If Log₄ (x) = 12, then log₂ (x / 4) is equal to

A. 11
B. 48
C. -12
D. 22
Questions 4:

The population of a country increased by an average of 2% per year from 2000 to 2003. If the population of this country was 2 000 000 on December 31, 2003, then the population of this country on January 1, 2000, to the nearest thousand would have been

A. 1 846 000
B. 1 852 000
C. 1 000 000
D. 1 500 000
Questions 5:

f is a quadratic function whose graph is a parabola opening upward and has a vertex on the x-axis. The graph of the new function g defined by g(x) = 2 - f(x - 5) has a range defined by the interval

A. [ -5 , + infinity)
B. [ 2 , + infinity)
C. ( - infinity , 2]
D. ( - infinity , 0]
Questions 6:

f is a function such that f(x) < 0. The graph of the new function g defined by g(x) = | f(x) | is a reflection of the graph of f

A. on the y axis
B. on the x axis
C. on the line y = x
D. on the line y = - x
Questions 7:

If the graph of y = f(x) is transformed into the graph of 2y - 6 = - 4 f(x - 3), point (a , b) on the graph of y = f(x) becomes point (A , B) on the graph of 2y - 6 = - 4 f(x - 3) where A and B are given by

A. A = a - 3, B = b
B. A = a - 3, B = b
C. A = a + 3, B = -2 b
D. A = a + 3, B = -2 b +3
Questions 8:

When a parabola represented by the equation y - 2x² = 8 x + 5 is translated 3 units to the left and 2 units up, the new parabola has its vertex at

A. (-5 , -1)
B. (-5 , -5)
C. (-1 , -3)
D. (-2 , -3)
Questions 9:

The graphs of the two linear equations ax + by = c and bx - ay = c, where a, b and c are all not equal to zero,

A. are parallel
B. intersect at one point
C. intersect at two points
D. perpendicular
Questions 10:

The graphs of the two equations y = a x² + b x + c and y = A x² + B x + C, such that a and A have different signs and that the quantities b² - 4 a c and B² - 4 A C are both negative,

A. intersect at two points
B. intersect at one point
C. do not intersect
D. none of the above
Questions 11:

For x greater than or equal to zero and less than or equal to 2 pi, sin x and cos x are both decreasing on the intervals

A. (0 , pi/2)
B. (pi/2 , pi)
C. (pi , 3 pi / 2)
D. (3 pi / 2 , 2 pi)
Questions 12:

The three solutions of the equation f(x) = 0 are -2, 0, and 3. Therefore, the three solutions of the equation f(x - 2) = 0 are

A. - 4, -2, and 1
B. -2, 0 and 3
C. 4, 2, and 5
D. 0, 2 and 5
Questions 13:

The three solutions of the equation f(x) = 0 are - 4, 8, and 11. Therefore, the three solutions of the equation f(2 x) = 0 are

A. - 2, 4, and 11/2
B. - 8, 16 and 22
C. - 4, 8, and 11
D. 2, 19 / 2 and 7 / 2
Questions 14:

A school committee consists of 2 teachers and 4 students. The number of different committees that can be formed from 5 teachers and 10 students is

A. 10
B. 15
C. 2100
D. 8
Questions 15:

Five different books (A, B, C, D and E) are to be arranged on a shelf. Books C and D are to be arranged first and second starting from the right of the shelf. The number of different orders in which books A, B and E may be arranged is

A. 5!
B. 3!
C. 2!
D. 3! * 2!
Questions 16:

The mean of a data set is equal to 10 and its standard deviation is equal to 1. If we add 5 to each data value, then the mean and standard deviation become

A. mean = 15 , standard deviation = 6
B. mean = 10 , standard deviation = 6
C. mean = 15 , standard deviation = 1
D. mean = 10 , standard deviation = 1
Questions 17:

The exam scores of all 500 students were recorded and it was determined that these scores were normally distributed. If Jane's score is 0.8 standard deviation above the mean, then how many, to the nearest unit, students scored above Jane?

A. 394
B. 250
C. 400
D. 106
Questions 18:

If f(x) is an odd function, then | f(x) | is

A. an odd function
B. an even function
C. neither odd nor even
D. even and odd
Questions 19:

The period of | sin (3x) | is

A. 2 pi
B. 2 pi / 3
C. pi / 3
D. 3 pi
Questions 20:

When a metallic ball bearing is placed inside a cylindrical container, of radius 2 cm, the height of the water, inside the container, increases by 0.6 cm. The radius, to the nearest tenth of a centimeter, of the ball bearing is

A. 1 cm
B. 1.2 cm
C. 2 cm
D. 0.6 cm
Questions 21:

The period of 2 sin x cos x is

A. 4 pi²
B. 2 pi
C. 4 pi
D. pi
Questions 22:

The probability that an electronic device produced by a company does not function properly is equal to 0.1. If 10 devices are bought, then the probability, to the nearest thousandth, that 7 devices function properly is

A. 0.057
B. 0.478
C. 0.001
D. 0

ANSWERS TO ABOVE QUESTIONS

1b, 2c, 3d, 4a, 5c, 6b, 7d, 8a, 9d, 10c

11b, 12d, 13a, 14c, 15b, 16c, 17d, 18b, 19c, 20b

21d, 22a.

1. What is the next prime number after 7?

2. The perimeter of a circle is also known as what?

3. 65 – 43 = ?

4. True or false? A convex shape curves outwards.

5. What does the square root of 144 equal?

6. True or false? Pi can be correctly written as a fraction.

7. What comes after a million, billion and trillion?

8. 52 divided by 4 equals what?

9. What is the bigger number, a googol or a billion?

10. True or false? Opposite angles of a parallelogram are equal.

11. 87 + 56 = ?

12. How many sides does a nonagon have?

13. True or false? -2 is an integer.

14. What is the next number in the Fibonacci sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ?

15. 7 x 9 = ?

16. True or false? In an isosceles triangle all sides are unequal.

17. In statistics, the middle value of an ordered set of values is called what?

18. What does 3 squared equal?

19. True or false? -4 is a natural number.

20. 5 to the power of 0 equals what?

Math Quiz Answers

1. 11	2. The circumference	3. 22	4. True
5. 12	6. False	7. A quadrillion	8. 13
9. A googol	10. True	11. 143	12. 9
13. True	14. 55	15. 63	16. False (2 sides are equal)
17. The median	18. 9	19. False	20. 1

Physics Objective Question

123 10:40 PM Objective Question, Questions, Science No comments

Objective Question Of Physics

1.	A certain current on passing through a galvanometer produces a deflection of 100 divisions. When a shunt of one ohm is connected, the deflection reduces to 1 division. The galvanometer resistance is (A) 100 W (B) 99 W (C) 10 W (D) 9.9 W	Answer: (B)
2.	A closed organ pipe and an open organ pipe of same length produce 2 beats/second while vibrating in their fundamental modes. The length of the open organ pipe is halved and that of closed pipe is doubled. Then, the number of beats produced per second while vibrating in the fundamental mode is ______. (A) 8 (B) 7 (C) 2 (D) 6	Answer: (B)
3.	A convex and a concave lens separated by distance d are then put in contact. The focal length of the combination (A) decreases (B) increases (C) becomes 0 (D) remains the same	Answer: (B)
4.	A current of 5A is flowing at 220 V in the primary coil of a transformer. If the voltage produced in the secondary coil is 2200 V and 50% of power is lost, then the current in the secondary will be (A) 2.5 A (B) 5 A (C) 0.25 A (D) 0.5 A	Answer: (C)

6.	A horizontal metal wire is carrying an electric current from the north to the south. Using a uniform magnetic field, it is to be prevented from falling under gravity. The direction of this magnetic field should be towards the______. (A) east (B) west (C) north (D) south	Answer: (A)

8.	A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it (A) increases, thermal velocity of the electron decreases (B) decreases, thermal velocity of the electron decreases (C) increases, thermal velocity of the electron increases (D) decreases, thermal velocity of the electron increases	Answer: (D)
9.	A motorboat covers a given distance in 6 hours moving downstream on a river. It covers the same distance in 10 hours moving upstream. The time it takes to cover the same distance in still water is ______. (A) 6.5 hours (B) 8 hours (C) 9hours (D) 7.5 hours	Answer: (D)
10.	A radioactive sample S₁ having the activity A₁ has twice the number of nuclei as another sample S₂ of activity A₂. If A₂ = 2A₁, then the ratio of half life of S₁ to the half life of S₂is (A) 0.25 (B) 0.75 (C) 4 (D) 2	Answer: (C)
11.	A body of mass M hits normally a rigid wall with velocity V and bounces back with the same velocity. The impulse experienced by the body is (A) Zero (B) MV (C) 1.5 MV (D) 2 MV	Answer: (D)
12.	A body projected vertically from the earth reaches a height equal to earth's radius before returning to the earth. The power exerted by the gravitational force is greatest (A) At the instant just after the body is projected (B) At the highest position of the body (C) At the instant just before the body hits the earth (D) It remains constant all through	Answer: (C)
13.	A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled, then the outward electric flux will (A) Be doubled (B) Increase four times (C) Be reduced to half (D) Remain the same	Answer: (D)
14.	A convex lens of focal length 30 cm produces 5 times magnified real image of an object. What is the object distance? (A) 36 cm (B) 25 cm (C) 30 cm (D) 150 cm	Answer: (A)
15.	A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is _______. (A) 20 min (B) 30 min (C) 80 min (D) 120 min	Answer: (A)


2.			Two beams of red and violet colours are made to pass separately through a prism of A = 60°. In the minimum deviation position, the angle of refraction inside the prism will be (A) greater for violet colour (B) 30° for both the colours (C) greater for red colour (D) equal but not 30° for both the colours	Answer: (B)
3.			₉₂U²³⁵ undergoes successive disintegrations with the end product of ₈₂Pb²⁰³. The Number of a and b particles emitted are (A) a = 6, b = 4 (B) a = 6, b = 0 (C) a = 8, b = 6 (D) a = 3, b = 3	Answer: (C)
4.			A bat flies at a steady speed of 4 ms^-¹ emitting a sound of f = 90 ´ 10³Hz. It is flying horizontally towards a vertical wall. The frequency of the reflected sound as detected by the bat will be _____. (Take velocity of sound in air as 330 ms^-¹). (A) 92.1 ´ 10³ Hz (B) 89.1 ´ 10³ Hz (C) 88.1 ´ 10³ Hz (D) 87.1 ´ 10³ Hz	Answer: (A)
5.			A battery of e.m.f. E has an internal resistance 'r'. A variable resistance R is connected to the terminals of the battery. A current I is drawn from the battery. V is the terminal P.D. lf R alone is gradually reduced to zero, which of the following best describes I and V? (A) I approaches E / r, V approaches E (B) I approaches infinity, V approaches E (C) I approaches zero, V approaches E (D) I approaches E / r, V approaches zero	Answer: (D)
6.			A boat has green light of wavelength l = 500 nm on the mast. What wavelength would be measured and what colour would be observed for this light as seen by a diver submerged in water by the side of the boat? Given n_w = 4/3. (A) Green of wavelength 500 nm (B) Blue of wavelength 376 nm (C) Green of wavelength 376 nm (D) Red of wavelength 665 nm	Answer: (C)

8.			A body of mass 4 kg is accelerated upon by a constant force, travels a distance of 5 m in the first second and a distance of 2 m in the third second. The force acting on the body is (A) 2 N (B) 4 N (C) 6N (D) 8N	Answer: (C)
9.			A body weighs 50 grams in air and 40 grams in water. How much would it weigh in a liquid of specific gravity 1.5? (A) 30 grams (B) 35 grams (C) 65 grams (D) 45 grams	Answer: (B)
10.			A capacitor and an inductance coil are connected in separate AC circuits with a bulb glowing in both the circuits. The bulb glows more brightly when ______. (A) separation between the plates of the capacitor is increased. (B) a dielectric is introduced into the gap between the plates of the capacitor. (C) an iron rod is introduced into the inductance coil. (D) the number of turns in the inductance coil is increased.	Answer: (B)
11.			A bar magnet is equivalent to _______. (A) solenoid carrying current (B) circular coil carrying current (C) toroid carrying current (D) straight conductor carrying current	Answer: (A)
12.			A beam of light of wavelength 600 nm from a distant source falls on a single slit 1mm wide and the resulting diffraction pattern is observed on a screen 2m away. The distance between the first dark fringes on either side of the central bright fringe is _______. (A) 1.2 mm (B) 1.2 cm (C) 2.4 cm (D) 2.4 mm	Answer: (D)
13.			A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is _______. (A) the focal point shifts away from the lens by a small distance. (B) the focus remains undisturbed. T (C) the focus shifts to infinity. (D) the focal point shifts towards the lens by a small distance.	Answer: (C)
14.			A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describe best the image formed of an object of height 2 cm placed 30 cm from the lens? (A) Real, inverted, height = 1 cm (B) Virtual, upright, height = 1 cm (C) Virtual, upright, height = 0.5 cm (D) Real, inverted, height = 4 cm	Answer: (D)
15.			A body of mass 5 kg is thrown vertically up with a kinetic energy of 490 J. The height at which the kinetic energy of the body becomes half of the original value is ______. (A) 12.5 m (B) 10 m (C) 2.5 m (D) 5 m	Answer: (D)
	1.	A ray of light enters from a rarer to a denser medium. The angle of incidence is i. Then the reflected and refracted rays are mutually perpendicular to each other. The critical angle for the pair of media is (A) Sin^-¹(Tan i) (B) Tan^-¹(Sin i) (C) Sin^-¹(Cot i) (D) Cos^-¹(Tan i)			Answer: (C)
	2.	A simple pendulum is suspended from the ceiling of a lift. When the lift is at rest its time period is T. With what acceleration should the lift be accelerated upwards in order to reduce its period to T /2? (g is acceleration due to gravity). (A) 2g (B) 3g (C) 4g (D) g			Answer: (B)

	4.	A string vibrates with a frequency of 200 Hz. When its length is doubled and tension is altered, it begins to vibrate with a frequency of 300 Hz. The ratio of the new tension to the original tension is (A) 9 : 1 (B) 1 : 9 (C) 3 : 1 (D) 1 : 3			Answer: (A)
	5.	A train is moving slowly on a straight track with a constant speed of 2 ms^-¹. A passenger in that train starts walking at a steady speed of 2 ms^-¹ to the bank of the train in the opposite direction of the motion of the train. So to an observer standing on the platform directly in front of that passenger, the velocity of the passenger appears to be _____ . (A) 2 ms^-¹ in the opposite direction of the train (B) zero (C) 4 ms^-¹ (D) 2 ms^-¹			Answer: (B)

	7.	According to Einstein's photoelectric equation, the graph of K.E. of the photoelectron emitted from the metal versus the frequency of the incident radiation gives a straight line graph, whose slope ______. (A) is same for all metals and independent of the intensity of the incident radiation. (B) depends on the nature of the metal. (C) depends on the intensity of the incident radiation. (D) depends on the nature of the metal and also on the intensity of incident radiation.			Answer: (A)
	8.	An astronaut on a strange planet finds that acceleration due to gravity is twice as that on the surface of Earth. Which of the following could explain this? (A) Both the mass and radius of the planet are twice as that of Earth. (B) Mass of the planet is half as that of Earth, but radius is same as that of Earth. (C) Both the mass and radius of the planet are half as that of Earth. (D) Radius of the planet is half as that of Earth, but the mass is the same as that of Earth.			Answer: (C)


2.	Two similar circular loops carry equal currents in the same direction. Un moving the coils further apart, the electric current will (A) increase in both (B) decrease in both (C) remain unaltered (D) increases in one and decreases in the second	Answer: (A)


	Two tangent galvanometers A and B are identical except in their number of turns. They are connected in series. On passing a current through them, deflections of 600 and 300 are produced. The ratio of the number of turns in A and B is (A) 1 : 3 (B) 3 : 1 (C) 1 : 2 (D) 2 : 1	Answer: (B)
6.	Water is in streamline flow along a horizontal pipe with nonuniform cross-section. At a point in the pipe where the area of cross-section is 10 cm², the velocity of water is 1 ms^-¹ and the pressure is 2000 Pa. The pressure at another point where the cross-sectional area is 5 cm² is ______. (A) 1000 Pa (B) 500 Pa (C) 4000 Pa (D) 2000 Pa	Answer: (B)
7.	What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film = 1.5, wavelength of the light incident on the film = 600 nm. (A) 50 nm (B) 200 nm (C) 100 nm (D) 300 nm	Answer: (C)
8.	When a neutron is disintegrated to give a b-particle, ______. (A) a proton alone is emitted. (B) a proton and an antineutrino are emitted. (C) a neutrino alone is emitted. (D) a proton and neutrino are emitted.	Answer: (B)

10.	Which of the following is a dichroic crystal? (A) Quartz (B) Tourmaline (C) Mica (D) Selenite	Answer: (B)

Art, religion and science do not necessarily contradict one another because
1. all three have different and mutually exclusive domains
2. the only rational course is to choose science and reject religion and art
3. the only rational course is to choose science and art and reject religion
4. if you choose science, you should reject religion and art
5. if you choose religion you should reject science
6. the three can legitimately work to complement and enrich one another
7. if you choose art you should reject science
8. if you choose art you should reject religion
A frame-work that is used to synthesize a collection of hypotheses and related information is called a
1. hypothesis
2. fact
3. theory
4. law
5. principle
6. science
7. all of the above
8. none of the above
Being knowledgeable about science, the arts, and religion, makes a person
1. very confused
2. truly educated
3. very arrogant
4. very intelligent
5. all of the above
6. none of the above
A scientific hypothesis is
1. a theory
2. a hypothesis
3. a frame-work
4. a law
5. a principle
6. an educated guess
7. a fact
The difference between science and technology is that technology deals more with
1. space aliens
2. development of scientific theories to address human needs
3. establishment of scientific institutions to address human needs
4. discovery of scientific laws to address human needs
5. application of scientific principles to address human needs
6. destruction of opposing scientific theories
7. leprechauns
An object falls out of an airplane, and falls freely downward. Its
1. mass increases
2. acceleration increases
3. velocity increases
4. gravity increases
5. mass decreases
6. velocity decreases
7. acceleration decreases
You brake suddenly. The passengers in your car lurch forward. This demonstrates
1. gravity
2. mass
3. weight
4. length
5. good driving
6. inertia
7. that a leprechaun was crossing the road
A truck is travelling at 10 m/s. A package drops off the truck. Neglecting air resistance, as the package hits the ground, its horizontal speed is
1. 0 m/s
2. 10 m/s
3. 20 m/s
4. depends on the height of the truck
5. depends on the weight of the package
6. depends on the color of the package
7. 100 m/s
A truck is decelerating. A package is dropped from the midpoint of the ceiling of the truck's storage compartment. The package hits the floor
1. immediately beneath the midpoint of the ceiling
2. closer to the back of the truck than the midpoint
3. closer to the front of the truck than the midpoint
4. all of the above
5. none of the above
You tie a rock to a string and whirl it in a horizontal circle. The string breaks. In the absence of gravity, the rock
1. travels in a circle
2. falls in a straight line down to the earth
3. flies in a straight line vertically up into the air
4. travels in a straight line horizontally away from you
5. falls in a parabola to the earth
6. immediately stops moving
7. explodes
A freely falling object started from rest. 2 seconds later, its speed is about
1. 5 m/s
2. 10 m/s
3. 15 m/s
4. 20 m/s
5. 25 m/s
6. 30 m/s
7. 35 m/s
A base ball is hit straight up into the air at a speed of 20 m/s. How long does it take to reach the high-point in its trajectory.
1. 1/2 seconds
2. 1 second
3. 2 seconds
4. 4 seconds
5. 5 seconds
6. 10 seconds
7. 20 seconds
Galileo used inclined planes to ____ the effective acceleration (of a rolling cylinder or ball) compared to earth's gravity
1. increase
2. stop
3. decrease
4. keep the same
5. none of the above
6. all of the above
A baseball is hit vertically upward at 30 m/s. One second later its speed is about ____ vertically upward.
1. 30 m/s
2. 35 m/s
3. 40 m/s
4. 25 m/s
5. 20 m/s
6. 15 m/s
7. 10 m/s
8. 0 m/s
A ball is thrown upwards and caught once it comes back down. The speed of the ball as it returns and is caught is ___ if there is air resistance compared to if there were no air resistance.
1. greater
2. the same
3. double
4. zero
5. infinite
6. lower
7. none of the above
The force of gravity acting on a 100 kg person is ___ compared to the force of gravity on a 1 kg book
1. 4 times larger
2. the same
3. double
4. zero
5. 10 times larger
6. 100 times larger
7. lower
8. none of the above
There is only one force acting on an object. For the object to travel at constant velocity, this force must be
1. a constant non-zero value
2. a varying non-zero value
3. a constant zero value
4. a positive value
5. a negative value
6. none of the above
An object's mass is increasing while its acceleration is constant. The force applied to the object must
1. be increasing
2. be decreasing
3. stay the same
4. increase and then decrease
5. decrease and then increase
6. none of the above
An object is moving in a circle with constant speed. The object has
1. a constant velocity
2. zero acceleration
3. a constant acceleration
4. zero velocity
5. no forces acting on it
6. no net force acting on
7. changing velocity but constant acceleration
8. changing velocity and acceleration
A man weighs 900 N, and is standing with his feet across three bathroom scales so his weight is equally shared among the three scales. The reading on each scale is
1. 900 N
2. 2700 N
3. 300 N
4. 90 N
5. 30 N
6. none of the above
A pebble flies up and hits the windshield of a truck travelling at 80 km/hr. The force of the impact is
1. greater on the pebble
2. lesser on the pebble
3. greater on the pebble than on the windshield, if the pebble shatters
4. greater on the windshield than on the pebble, if the windshield shatters
5. the same on pebble and on the windshield
6. none of the above
As a meteor falls towards earth, it is attracted by earth's gravity. What is the reaction to this force?
1. air resistance
2. the meteor's inertia
3. the earth's inertia
4. the earth's gravity
5. earth is attracted by the meteor's gravity
6. the meteor is attracted by all the particles in the universe
7. earth is attracted by all the particles in the universe
A person who has a mass of 100 kg is attracted to the earth by a force of about 1000 N. The force with which this person attracts the earth is
1. zero
2. much smaller
3. 10 N
4. 100 N
5. 500 N
6. 1000 N
7. 2000 N
8. none of the above
Two people are in a tug-of-war. Each person pulls the rope with a force of 500 N. What is the tension in the rope?
1. 1000 N
2. zero
3. 250 N
4. 500 N
5. depends on the diameter of the rope
6. none of the above
Every force has an equal and opposite reaction. A force and its reaction
1. cancel each other
2. are two interactions
3. are parts of a single interaction
4. have double the effect compared to a force without its reaction
5. none of the above
A 7-year old child and a 21-year old college student pull as hard as they can on opposite ends of a rope in a tug-of war. The force is applied to the rope by the child is ___ compared to the force applied by the college student.
1. smaller
2. the same
3. larger
4. depends on how strong the child is
5. none of the above
A railroad car that is initially at rest is hit by an identical railroad car traveling with a momentum of 100 units. The cars stick together and move down the railroad tracks. The combined momentum of the cars after the collision is
1. 200 units
2. 100 units
3. 50 units
4. 0 units
5. none of the above
An athlete performs a high jump. As she lands, she bends her knees as she reaches the ground. This increases the time of impact. The result is to ___ the force that her body experiences.
1. increase
2. keep the same
3. reduce
4. the answer depends on how high she jumped
5. none of the above
A canon ball travelling at 10 m/s has a momentum of 50 kg m/s. What is the mass of the ball?
1. 10 kg
2. 50 kg
3. 20 kg
4. 5 kg
5. 25 kg
6. none of the above
A car travelling at 10 km/hr runs into a haystack and comes to a stop. This is less dangerous than if the car had driven into a concrete wall. This is because driving into the haystack results in
1. reduced impulse
2. increased impulse
3. the same impulse
4. reduced change in momentum
5. increased change in momentum
6. the same change in momentum
7. increased time of impact and reduced impact force
8. increased time of impact and increased impact force
9. reduced time of impact and reduced impact force
10. reduced time of impact and increased impact force
You accelerate. The speed of your car doubles. Which of the following items quadruples as a result?
1. momentum
2. potential energy
3. acceleration
4. kinetic energy
5. all of these
6. none of these
Two railroad cars move towards each other at 10 m/s. They collide and bounce backward at 20 m/s. This event violates conservation of
1. mass
2. acceleration
3. kinetic energy
4. potential energy
5. collisions
6. none of these
7. all of these
A certain car has momentum. It therefore must also have
1. acceleration
2. kinetic energy
3. force
4. potential energy
5. impulse
6. none of these
7. all of these
A 100 Newton force is used to push a table by 5 meters. The amount of work done on the table is
1. 5 J
2. 100 J
3. 0 J
4. 500 J
5. 1000 J
A meteor moving at 30 m/s collides with a twice-as-massive meteor and sticks to it. After the collision, the combined meteors have a kinetic energy that is ___ as much as the total kinetic energy before the collision.
1. the same
2. twice
3. one third
4. three quarters
5. two thirds
6. not enough information
A farmer replaces the tires on his tractor with smaller diameter tires. For a given RPM, the linear speed of the tractor is now
1. the same as before
2. more
3. less
4. all of the above
5. none of the above
6. not enough information
Based on rotational inertia, which will take longer to roll down an incline… a can filled with ice, or the same can filled with water?
1. ice
2. water
3. both the same
4. depends on the size of the can
5. depends on the temperature of the water
6. not enough information
If you kick a football so that the force of your kick passes through its center of gravity. As it flies through the air, the football will
1. not move
2. rotate clockwise
3. rotate counter-clockwise
4. rotate from left to right
5. not rotate
6. not enough information
As you slow down your car, the rotational speed of your tires is halved. The linear speed of a bug sitting at the edge of your tire will
1. double
2. quadruple
3. stay the same
4. be halved
5. be reduced to a quarter
During an ice age, the polar ice caps grow in size and the water-level drops in the oceans all around the earth. This redistribution of mass will cause the earth's day to become
1. longer
2. shorter
3. stay the same
4. the earth will stop rotating
5. not enough information
If the mass of the sun and the earth are both tripled, and the distance between them is also tripled, the force between them will be
1. doubled
2. halved
3. tripled
4. one third
5. the same
6. nine times
7. one ninth
You don’t see tides in your swimming pool. This is because
1. your contact lenses are missing
2. magnetic forces hold the water down
3. the pool is too shallow for tides
4. the pool is too deep for tides
5. the tides happen at night when you are asleep
6. all parts of the pool are at about the same distance to the moon
The distance between the earth and the moon is reduced to one third. The gravitational force between them becomes
1. 3 times bigger
2. 3 times smaller
3. 9 times bigger
4. 9 times smaller
5. stays the same
What keeps the earth from falling into the sun?
1. strings hold the earth up
2. gravity holds the earth up
3. the earth's tangential speed
4. smoke and mirrors
5. the sun's gravity is zero where the earth is
What is a black hole ?
1. a hole in your dry-wall
2. space with no stars
3. space with no light
4. space with no mass
5. a space with mass so highly concentrated that even light cant escape the resulting gravity
A ball is thrown horizontally. After it has left the thrower's hand, what is the acceleration that it experiences ?
1. an acceleration of - 1 g horizontally
2. an acceleration of + 1 g horizontally
3. 1 g downward
4. 1 g upward
5. no acceleration
A pitcher drops a ball. At the same instant, another ball is thrown at an angle of 5 degrees below the horizontal. Which ball will hit the ground first ?
1. the dropped ball
2. the thrown ball
3. both reach at the same time
4. the dropped ball turns into a banana and flies away
A meteor is captured by earth's gravitational field and goes into elliptical orbit around the earth. Compared to when the meteor is far from the earth, its speed when it is close to the earth is
1. the same
2. faster
3. slower
4. not enough information
5. depends on whether today is Tuesday or Thursday
A student throws a ball horizontally from the top of a 20 meter tall building. The ball hits the ground 20 m from the building. What was the students pitching speed?
1. 20 m/s
2. 1 m/s
3. 5 m/s
4. 10 m/s
5. not enough information
What keeps the moon from falling?
1. earth's gravity is zero near the moon
2. earth's gravity is balanced by the sun's gravity
3. strings, smoke and mirrors
4. magnetic forces
5. electrical forces
6. the moon is falling around the earth
Why are the atoms in a baby's body about the same age as the atoms in an adult's body? Because…
1. Inside every baby is an adult
2. Inside every adult is a baby
3. Atoms are eternal, i.e., they always existed
4. All atoms and elements were formed at the Big Bang, about 14 billion years ago
5. Atoms, that are present in both baby and adult, were formed about the same time by exploding stars
Most of the mass of an atom is in its
1. electrons
2. massons
3. atomic mass units
4. protons and neutrons
5. miceons
The atoms in your body are mostly empty space, and so are the atoms in any wall. Why then is your body unable to pass through walls ? Because of…
1. absence of doors in the walls
2. magnetic forces between atoms
3. nuclear forces
4. gravitational forces
5. electrical forces
6. atomic vibrations
Which of the following is a mixture?
1. water
2. carbon-dioxide
3. methane
4. air
5. salt
6. sugar
7. none of the above
8. all of the above
When sodium and chlorine react to form salt, a certain amount of energy is given off. This energy is ___ compared to the energy it takes to separate sodium and chlorine to form salt.
1. less
2. more
3. the same
4. it is impossible to separate sodium and chlorine from salt
Which has more surface area?
1. a whole potato
2. a potato cut into four quarters
3. a potato cut into Freedom fries (ex-French fries)
4. all of these have the same surface area
Doubling the length of the sides of a cube multiplies its volume by
1. 2 and its surface area by 1
2. 4 and its surface area by 2
3. 6 and its surface area by 3
4. 8 and its surface area by 4
5. does not change its volume
Halving the diameter of a rope will multiply its strength by
1. 1
2. 1/2
3. 1/4
4. 1/8
5. 2
6. 4
7. not enough information
Which has greater surface area for a given body weight (i.e., greater surface area per unit weight)
1. a snake
2. an elephant
3. a bowling ball
4. a piece of string
5. not enough information
An object has a mass of 60 kg and a density of 30 kg per cubic meter. What is the volume of the object?
1. 1800 cubic meters
2. 2 cubic meters
3. 30 cubic meters
4. 60 cubic meters
5. not enough information
You submerge a gallon jug in your swimming pool. Where is the water pressure the greatest?
1. left side of the jug
2. right side of the jug
3. top of the jug
4. middle of the jug
5. bottom of the jug
6. all of the above
7. none of the above
You have a sheet of rolled out dough. You roll this up into a ball. Doing this reduces its
1. mass
2. momentum
3. volume
4. surface area
5. all of the above
6. none of the above
Fill the compartments of an ice-cube tray half full with iron nails. Top off with water and freeze. Now drop one of these ice cubes in a glass of water. As it melts, the water level in the glass will
1. drop
2. rise
3. stay the same
4. all of the above
An iceberg is partly immersed, as it floats in the ocean. It is buoyed up by
1. leprechauns
2. the gravitational attraction from the moon
3. a force equal to the weight of the iceberg
4. a force less than the weight of the iceberg
5. a force greater than the weight of the iceberg
6. a force equal to twice the weight of the water that is displaced
7. all of the above
8. none of the above
The buoyant force is the smallest on a completely immersed
1. 2 cubic centimeter block of iron
2. 2 cubic centimeter block of aluminum
3. 2 cubic centimeter block of wood
4. the force is the same on all three blocks
5. none of the above
6. not enough info
A Helium filled balloon is released and rises up into the sky. As it moves upward, it
1. becomes heavier
2. becomes smaller
3. becomes bigger
4. stays the same size
5. not enough information
A metal gas can will float up into the air if you fill it with
1. sand
2. water
3. air
4. helium
5. nitrogen
6. all of the above
7. none of the above
A pair of Magdeburg hemispheres are placed in contact and then evacuated. In which of the following situations would it take the most force to pull them apart
1. out in space
2. at the top of the earth's atmosphere
3. at sea level
4. 1 km beneath the ocean surface
5. 5 km below the ocean surface
A balloon filled with air is tied to a diver's helmet with a 1 foot long string. As the diver dives to the bottom of a deep lake, the balloon
1. expands
2. contracts
3. expands and then contracts
4. contracts and then expands
5. alternates between expansion and contraction
6. stays the same volume
7. all of the above
As a steady wind rushes over a pointed roof, the pressure above the roof is
1. higher
2. lower
3. the same
4. alternates between higher and lower
5. all of the above
If you were to measure out a plot of land on a very cold day the resulting plot would be ___ if you used a cloth tape-measure compared to a steel tape-measure.
1. larger
2. smaller
3. the same
4. none of the above
5. all of the above
To reduce the odds of your radiator coolant freezing in the winter, let's say that you add a chemical that changes the specific-heat of the coolant. You want the specific heat to
1. increase
2. decrease
3. stay the same
4. none of the above
5. all of the above
You hide your gold ring in your freezer. As the ring drops in temperature, the hole inside the ring becomes
1. larger
2. smaller
3. stays the same
4. none of the above
5. all of the above
The boiling point of water is 100 degrees C. What would this be on a Kelvin scale?
1. 100 K
2. 73 K
3. 173 K
4. 273 K
5. 373 K
6. 473 K
7. 573 K
You fill a glass bottle with water and put it in your freezer. The next morning you find that the bottle has shattered. This is because
1. the bottle expanded
2. the bottle contracted
3. the water expanded when it froze in the bottle
4. the water contracted when it froze in the bottle
5. leprechauns in the freezer
6. space aliens from mars
Copper and aluminum have outer electrons that are loosely bound to the atoms. This makes these elements
1. poor electrical conductors
2. expensive
3. pure
4. slippery
5. good electrical conductors
6. all of the above
7. none of the above
Radiation from the star "Betelgeuse" is of longer wavelength than the sun. This means that the sun is ___ compared to that star.
1. cooler
2. hotter
3. at the same temperature
4. larger
5. smaller
6. bluer
At the same temperature, molecules of hydrogen have ___ speed compared to molecules of oxygen.
1. higher
2. lower
3. the same
4. no
5. infinite
At 350 degrees C, your oven radiates with a wavelength that is ___ compared to your stove top that is 500 C.
1. shorter
2. longer
3. the same
4. none of the above
5. all of the above
To reduce the odds of being burned, would you choose to walk rapidly across a bed of red hot
1. coal
2. iron
3. gold
4. aluminum
5. all of the above
When water freezes it
1. absorbs energy
2. gives off energy
3. neither
4. both
You wet your finger before you briefly touch a clothes iron. The protection (from wetting your finger) would be higher if the "heat of vaporization" of the water is
1. higher
2. lower
3. the same
4. zero
5. all of the above
When a metal is heated until it vaporizes, it
1. absorbs energy
2. gives off energy
3. neither
4. both
As your neighborhood pond is in the process of freezing over, it ___ the surrounding air.
1. cools
2. warms
3. neither cools nor warms
4. both warms and cools
Water at 0 degrees C will warm up faster than ice at 0 degrees C, because
1. water is more liquid
2. ice is more solid
3. ice absorbs heat when it melts
4. ice gives out heat when it melts
5. water likes ice
6. there is no ice at the earth's equator
The pitch (frequency) of a car's horn ___ as the car drives past you.
1. rises
2. drops
3. stays the same
4. all of the above
5. none of the above
The frequency of a pendulum on a high-gravity planet is ____ compared to the frequency on a low-gravity planet.
1. higher
2. lower
3. the same
4. all of the above
5. none of the above
A buoy rises and falls by a total height of 2 meters on the open ocean. What is the amplitude of the waves.
1. 2 meters
2. 4 meters
3. 1 meter
4. 0.5 meters
5. 8 meters
6. all of the above
A star is moving towards our solar system. Based on the Doppler effect, the frequency of its light is shifted towards
1. blue
2. red
3. white
4. black
5. all of the above
For two waves to be in phase, a sufficient condition is that the waves have the same
1. amplitude
2. wavelength
3. frequency
4. speed
5. instants in time at which the wave amplitude is zero
Compressions and rarefactions are not present with
1. longitudinal waves
2. transverse waves
3. both of these
4. neither of these
5. not enough information provided
6. none of the above
7. all of the above
All other things being equal, the speed of a sound wave ____ if its wavelength increases.
1. increases
2. decreases
3. both of these
4. neither of these
5. not enough information provided
6. none of the above
7. all of the above
A 680-hertz wave with a wavelength of 1/2 meter travels in air with a speed of
1. 680 m/s
2. 6800 m/s
3. 340 m/s
4. 3400 m/s
5. 1/2 m/s
6. 1 m/s
You hear a lot of static from your radio. Is the static you hear more likely to result from receiving FM or AM radio waves?
1. FM
2. AM
3. Neither produces any static.
4. Both produce equal amounts of static.
5. not enough information provided
6. none of the above
7. all of the above
You see lightning flash in the distance, and hear the thunder 10 seconds later. Assuming that sound travels at 340 m/s through the air, how far away was the lightning strike?
1. 34 meters
2. 3.4 meters
3. 340 meters
4. 3.4 km
5. 34 km
6. 340 km
Two charges are separated by a distance of 1 meter, and experience a mutual repulsive force of 1 Newton. If the distance between the charges is changed to 2 meters, what is the resulting repulsive force?
1. 1 N
2. 2 N
3. 4 N
4. 8 N
5. 1/2 N
6. 1/4 N
7. 1/8 N
What does a lightning rod do?
1. Attracts lightning to your building
2. Repels lightning from your building
3. Collects electrons from your building
4. Collects protons from your building
5. Reduces charge buildup on your building
6. not enough information provided
7. none of the above
8. all of the above
Two charged particles are held at a certain distance from each other. When they are released, they move and the force on each particle decreases. The particles MUST both be
1. positive
2. negative
3. of the same sign
4. of opposite sign
5. not enough information provided
6. none of the above
7. all of the above
If the electrical potential of a single electron is 1-volt in an electrical field, what is the electrical potential of 10 electrons at the same spot in the field?
1. 10 volts
2. 100 volts
3. 1000 volts
4. 1 volt
5. 1/10 volts
6. 1/100 volts
A pith ball is suspended by a non-conducting fiber. When a positively charged rod is brought near the ball, but without touching it, the ball
1. becomes positively charged
2. becomes negatively charged
3. becomes lighter
4. becomes heavier
5. becomes depolarized
6. becomes polarized
What is the source of the electrons that heat up your clothes iron
1. a hydroelectric dam
2. a coal power plant
3. the power outlet in your home
4. a nuclear power plant
5. radioactivity in your clothes-iron
6. the moon shining on your clothes-iron
7. atoms in the filament of your clothes-iron
You buy a hair-dryer in another country and it is rated at 220 V. If you plug it into a 110 V outlet, the current in the dryer is ___ compared to if you plug it into a 220 V outlet.
1. the same
2. two times greater
3. four times greater
4. 110 times greater
5. half
6. a quarter
Three light-bulbs are connected in parallel across a battery. One has a thick filament, one a thin filament, and one a medium filament. Which one has the lowest voltage across the lamp.
1. Medium filament
2. thin filament
3. thick filament
4. there is no voltage across the filaments
5. voltage is the same across all three filaments
A light bulb is connected to a 200 V power source. A current of 2.0 Amps flows across the bulb. How much power is being dissipated by the bulb?
1. 200 W
2. 400 W
3. 100 W
4. 50 W
5. 800 W
6. none of the above
A voltage of 30 V is applied across a 30 ohm resistor. What is the current flowing through the resistor.
1. 0 Amps
2. 1 Amp
3. 2 Amps
4. 900 Amps
5. 300 Amps
6. 30 Amps
A magnetic field runs from the top of this page down to the bottom of this page. An electron is fired from left to right across the page. The electron is ___ by the magnetic field.
1. Indifferent to
2. attracted by
3. repelled by
4. attracted then repelled by
5. deflected out of the plane of the page
6. made to move in square patterns
A small piece of metal is attracted to a large magnet. The magnet is attracted to the small piece of metal with a force that is ____ compared to the force with which the metal is attracted to the magnet.
1. zero
2. infinite
3. very large
4. very small
5. the same
6. similar but not the same
A proton is travelling almost but not quite parallel to a magnetic field. An electron is travelling perpendicular to the same magnetic field. The force on the electron is ____ compared to the force on the proton.
1. zero
2. infinite
3. large
4. small
5. the same
6. similar but not the same
Magnetism is caused by
1. magnetons
2. magneticians
3. pieces of iron
4. pieces of gold
5. pieces of copper
6. moving magnetic charges
7. moving electric charges
Some of the planets in our Solar system have magnetic fields. The likely cause of these magnetic fields is
1. a reflection of the Sun's magnetic field
2. magnetons
3. magneticians
4. moving magnetic charges in the core of the planets
5. moving magnetic charges in the atmosphere of the planets
6. moving electric charges in the core of the planets
7. pieces of iron on the planets
8. pieces of gold on the planets
9. pieces of copper on the planets
Blue light has ___ wavelength compared to Red light.
1. the same
2. longer
3. zero
4. infinite
5. shorter
6. none of the above
Earth's atmosphere lets in most
1. infrared light
2. ultraviolet light
3. visible light
4. of any kind of radiation
5. none of the above
6. all of the above
Which of these waves have the longest wavelength?
1. infrared light
2. ultraviolet light
3. red light
4. blue light
5. X-rays
6. yellow light
7. radio waves
An electromagnetic wave has a wavelength of 1 m. What is its frequency?
1. 1 Hertz
2. 3 Hz
3. 300 Hz
4. 3000 Hz
5. 30,000 Hz
6. 300,000 Hz
7. 3,000,000 Hz
8. 300,000,000 Hz
If Proxima Centauri, our closest star, were to explode right now, it would take about 4 years for us to know about it because
1. it takes 4 years to build a big telescope to see the star
2. it takes 4 years to obtain funding to build the necessary telescope
3. the star is 4 years old
4. it takes 4 years for the light from this star to reach us
5. it takes 4 years for a signal from us to reach the star
6. it takes 4 years for us to travel by space-ship to the star
The colors on your computer monitor arise by color
1. mixing
2. multiplication
3. addition
4. division
5. subtraction
6. exponentiation
Sunsets can appear reddish due to
1. reflection from red smog in the air
2. reflection from blue smog in the air
3. reflection from red dust particles in the air
4. reflection from blue dust particles in the air
5. blue light being scattered away by small particles in the air
6. red light being scattered away by large particles
Clothes of a certain color can appear black in a room that is lit by a light that is
1. the same color as the clothes
2. the complementary color of the clothes
3. red in color
4. blue in color
5. white in color
6. the supplementary color of the clothes
Which will take longer to warm up in the summer sunlight
1. a white house
2. a black house
3. a brown house
4. a pink house
The sky is the clearest and deepest blue when there are ____ dust particles in the air
1. many
2. very few
3. very many
4. infinite numbers of
5. large sized
6. medium sized
Double the amplitude of a wave and you necessarily change its
1. wavelength
2. frequency
3. speed
4. color
5. taste
6. none of the above
7. all of the above
Charge carriers in a metal are not protons because protons are
1. neutral
2. positively charged
3. negatively charged
4. introverts
5. not very socially inclined
6. tightly bound
Connect three light-bulbs in parallel with a battery and you draw a certain amount of current. Connect the three light-bulbs in series with the same battery and you draw ____ current.
1. the same
2. more
3. less
4. zero
5. infinite
6. none of the above
7. all of the above
A steady magnetic field runs from top to bottom of this page. An electron is moving from bottom to top of this page. The force on the electron, exerted by the magnetic field, is
1. in the same direction as the electron's motion
2. in the opposite direction as the electron's motion
3. from left to right on this page
4. from right to left on this page
5. perpendicular to the plan of this page
6. zero
7. infinite
8. none of the above
A proton vibrates from side-to-side 10 times a second. It generates an electromagnetic field with a frequency of
1. 1 Hz
2. 2 Hz
3. 10 Hz
4. 100 Hz
5. 10 meters
6. 100 meters
7. 10 meters/second
8. 100 meters/second
To most efficiently absorb an electromagnetic wave, the frequency of the wave should be ___ the natural frequency of the material being used to absorb the wave.
1. greater than
2. less than
3. equal to
4. zero compared to
5. infinite compared to
6. none of the above
7. all of the above
When electron clouds in a material are made to oscillate ____ waves are necessarily emitted
1. electronic
2. magnetic
3. de Broglie
4. electromagnetic
5. sound
6. ocean
7. ultraviolet
A surface that appears smooth to one kind of waves can appear rough to another kind of waves whose wavelength is ____ compared to the first kind.
1. zero
2. infinite
3. smaller
4. larger
5. the same
6. all of the above
7. none of the above
The bottom of a swimming pool appears closer to the surface than it actually is. This is caused by ___ of light.
1. refraction
2. fraction
3. reflection
4. flection
5. absorption
6. sorption
7. denaturization
About 9 AM, in the morning, a beam of sunlight enters the water of your swimming pool. The beam necessarily bends ___ as it enters the water.
1. by zero degrees
2. by 180 degrees
3. by 90 degrees
4. towards the normal
5. away from the normal
6. none of the above
7. all of the above
Can longitudinal waves experience polarization?
1. No
2. yes
3. sometimes
4. Depends on the speed of the wave
5. depends on the frequency of the wave
6. depends on the amplitude of the wave
7. none of the above
8. all of the above
When the axes of two polaroid filters are perpendicular to each other ___ of the incoming light can pass through the combined filters
1. all
2. none
3. half
4. red frequencies
5. blue frequencies
6. white frequencies
7. slower photons
8. faster photons
An example of interefernce is
1. a mirage
2. light bending when it enters water
3. light bending when it exits water
4. red sunset
5. orange harvest moon
6. rainbow in the sky
7. rainbow colors in gasoline on water
If destructive interference eliminates red from white light, what color is the remaining light likely to be ?
1. red
2. brown
3. black
4. white
5. cyan
6. purple
7. yellow
Laser light is
1. incoherent
2. coherent
3. polychromatic
4. inchromatic
5. out of phase
6. sometimes in phase, sometimes out of phase
7. always red
An non-excited atom absorbs a single red photon, and then emits another photon. The emitted photon can be
1. blue
2. ultraviolet
3. violet
4. green
5. white
6. infrared
A material is heated so it is "red-hot". The atoms in the material are
1. not vibrating
2. vibrating at an infinite range of frequencies
3. vibrating at about the same frequency
4. oscillating in figures of eight
5. oscillating in circles
6. oscillating in squares
What is the primary source of the electromagnetic radiation that is continually emitted by your body?
1. your magnetic personality
2. your charm bracelet
3. radioactive atoms in your bones
4. your body temperature vibrates your atoms
5. your body clock
6. your most recent meal
Which of the following entities is most prone to being impacted by quantum effects
1. a whale
2. a horse
3. a meteor
4. a meteorite
5. an egg
6. an electron
7. a baseball
An ultraviolet laser beam and an infrared laser beam have the same number of photons. Which beam has the lower energy?
1. ultraviolet
2. infrared
3. both have the same energy
4. neither has any energy
5. depends on the speed of the ultraviolet light
6. depends on the frequency of the infrared light
7. all of the above
A photon's energy is given by its frequency multipled by ___ constant
1. Henry's
2. Jame's
3. Newton's
4. Einstein's
5. Planck's
6. phonton's
7. energy
The following entites are all moving at the same speed. Based on quantum physics, which of these entities has the shortest wavelength?
1. an elephant
2. a space-ship
3. an astronaut
4. a mouse
5. an insect
6. the earth
7. an electron
8. a proton
Light from an incandescent light bulb (e.g., in a table lamp) is
1. monochromatic
2. coherent
3. in phase
4. all of these
5. none of these
An atom absorbs a photon with 5 units of energy. It then emits a photon with an energy that can be
1. 10 units
2. 8 units
3. 7 units
4. 5 to 6 units
5. 5 or less units
6. 10 to 20 units
7. 20 units
A bar of iron is heated until it is "red hot". This means that
1. All of the energy of the bar is being radiated as heat
2. All of the energy of the bar is being radiated as infrared waves
3. its molecules are vibrating at an infinite range of rates
4. its molecules are vibrating at a wide (but not infinite) range of rates
5. its molecules are vibrating at nearly identical rates
6. its molecules are not vibrating because they are fixed in place
7. its molecules are not vibrating because only the electrons can vibrate
Which of the following is not emitting electromagnetic radiation
1. A radio transmitter antenna
2. A TV transmitter antenna
3. A red hot piece of iron
4. Molten lead
5. The surface of the sun
6. An ice cube
7. All of these
8. None of these
Quantum uncertainty has the greatest effect on
1. a car
2. a human
3. an atom
4. an electron
5. an elephant
6. a whale
7. a molecule
A beam of yellow light and a beam of ultraviolet light have the same total energy. Which has fewer photons ?
1. yellow beam
2. ultraviolet beam
3. both have the same number of photons
4. neither has any photons
5. it is impossible for a yellow beam and an ultraviolet beam to have the same total energy
6. there is no such thing as energy
A photon's energy divided by its frequency
1. is higher if the photon's energy is higher
2. is lower if the photon's energy is lower
3. is higher if the photon's frequency is higher
4. is higher if the photon's frequency is lower
5. is a constant called the photon constant
6. is a constant called Planck's constant
7. is a constant called the gravitational constant
8. is a constant called Maxwell's constant
An elephant and a mouse are moving at the same speed. Which has the smaller wavelength?
1. Neither has a wavelength
2. Both have the same wavelength
3. If they have the same interests, then they are on the same wavelength
4. Depends on if they are travelling in the same direction or in different directions
5. The elephant
6. The mouse
7. The kangaroo
Double the amplitude of a wave and you necessarily change its
1. wavelength
2. frequency
3. speed
4. color
5. taste
6. none of the above
7. all of the above
Charge carriers in a metal are not protons because protons are
1. neutral
2. positively charged
3. negatively charged
4. introverts
5. not very socially inclined
6. tightly bound
Connect three light-bulbs in parallel with a battery and you draw a certain amount of current. Connect the three light-bulbs in series with the same battery and you draw ____ current.
1. the same
2. more
3. less
4. zero
5. infinite
6. none of the above
7. all of the above
A steady magnetic field runs from top to bottom of this page. An electron is moving from bottom to top of this page. The force on the electron, exerted by the magnetic field, is
1. in the same direction as the electron's motion
2. in the opposite direction as the electron's motion
3. from left to right on this page
4. from right to left on this page
5. perpendicular to the plan of this page
6. zero
7. infinite
8. none of the above
A proton vibrates from side-to-side 10 times a second. It generates an electromagnetic field with a frequency of
1. 1 Hz
2. 2 Hz
3. 10 Hz
4. 100 Hz
5. 10 meters
6. 100 meters
7. 10 meters/second
8. 100 meters/second
To most efficiently absorb an electromagnetic wave, the frequency of the wave should be ___ the natural frequency of the material being used to absorb the wave.
1. greater than
2. less than
3. equal to
4. zero compared to
5. infinite compared to
6. none of the above
7. all of the above
When electron clouds in a material are made to oscillate ____ waves are necessarily emitted
1. electronic
2. magnetic
3. de Broglie
4. electromagnetic
5. sound
6. ocean
7. ultraviolet
A surface that appears smooth to one kind of waves can appear rough to another kind of waves whose wavelength is ____ compared to the first kind.
1. zero
2. infinite
3. smaller
4. larger
5. the same
6. all of the above
7. none of the above
The bottom of a swimming pool appears closer to the surface than it actually is. This is caused by ___ of light.
1. refraction
2. fraction
3. reflection
4. flection
5. absorption
6. sorption
7. denaturization
About 9 AM, in the morning, a beam of sunlight enters the water of your swimming pool. The beam necessarily bends ___ as it enters the water.
1. by zero degrees
2. by 180 degrees
3. by 90 degrees
4. towards the normal
5. away from the normal
6. none of the above
7. all of the above
Can longitudinal waves experience polarization?
1. No
2. yes
3. sometimes
4. Depends on the speed of the wave
5. depends on the frequency of the wave
6. depends on the amplitude of the wave
7. none of the above
8. all of the above
When the axes of two polaroid filters are perpendicular to each other ___ of the incoming light can pass through the combined filters
1. all
2. none
3. half
4. red frequencies
5. blue frequencies
6. white frequencies
7. slower photons
8. faster photons
An example of interefernce is
1. a mirage
2. light bending when it enters water
3. light bending when it exits water
4. red sunset
5. orange harvest moon
6. rainbow in the sky
7. rainbow colors in gasoline on water
If destructive interference eliminates red from white light, what color is the remaining light likely to be ?
1. red
2. brown
3. black
4. white
5. cyan
6. purple
7. yellow
Laser light is
1. incoherent
2. coherent
3. polychromatic
4. inchromatic
5. out of phase
6. sometimes in phase, sometimes out of phase
7. always red
An non-excited atom absorbs a single red photon, and then emits another photon. The emitted photon can be
1. blue
2. ultraviolet
3. violet
4. green
5. white
6. infrared
A material is heated so it is "red-hot". The atoms in the material are
1. not vibrating
2. vibrating at an infinite range of frequencies
3. vibrating at about the same frequency
4. oscillating in figures of eight
5. oscillating in circles
6. oscillating in squares
What is the primary source of the electromagnetic radiation that is continually emitted by your body?
1. your magnetic personality
2. your charm bracelet
3. radioactive atoms in your bones
4. your body temperature vibrates your atoms
5. your body clock
6. your most recent meal
Which of the following entities is most prone to being impacted by quantum effects
1. a whale
2. a horse
3. a meteor
4. a meteorite
5. an egg
6. an electron
7. a baseball
An ultraviolet laser beam and an infrared laser beam have the same number of photons. Which beam has the lower energy?
1. ultraviolet
2. infrared
3. both have the same energy
4. neither has any energy
5. depends on the speed of the ultraviolet light
6. depends on the frequency of the infrared light
7. all of the above
A photon's energy is given by its frequency multipled by ___ constant
1. Henry's
2. Jame's
3. Newton's
4. Einstein's
5. Planck's
6. phonton's
7. energy
The following entites are all moving at the same speed. Based on quantum physics, which of these entities has the shortest wavelength?
1. an elephant
2. a space-ship
3. an astronaut
4. a mouse
5. an insect
6. the earth
7. an electron
8. a proton
In the Bohr model, electrons can orbit the nucleus of an atom in a set of discrete rings. The perimeter of each ring corresponds to an integral number of ___ of the electron.
1. de Broglie spins
2. de Broglie rotations
3. de Broglie frequencies
4. de Broglie wavelengths
5. de Broglie flavors
6. de Broglie amplitudes
Alpha particles contain
1. protons
2. electrons
3. neutrons
4. alphons
5. particlons
6. positrons
7. gamma rays
The Bohr model of the atom has ___ circling the atomic nucleus.
1. protons
2. electrons
3. neutrons
4. alphons
5. particlons
6. positrons
7. gamma rays
Your hand and your table are both mostly empty space. Despite this, your hand does not pass through the table because
1. Your hand does not realize that it is mostly empty space
2. Your table does not realize that it is mostly empty space
3. Your table is not mostly empty space
4. Your hand is not mostly empty space
5. magnetic fields keep your hand from passing through the table
6. electric fields keep your hand from passing through the table
7. gravitational fields keep your hand from passing through the table
We encounter radioactivity during the course of our lives. Most of this exposure comes from
1. radios
2. TV
3. nuclear power plants
4. nuclear weapons testing
5. space ships
6. aliens
7. the natural environment
8. medical and dental X-rays
An alpha particle is absorbed by an atomic nucleus. If nothing else happens what changes in the nucleus.
1. the number of protons is reduced
2. the number of electrons is reduced
3. the number of neutrons is reduced
4. the number of protons is increased
5. the number of electrons is increased
6. the number of neutrons is increased
What happens if a Lithium atom emits an alpha particle? It becomes
1. a lithium isotope
2. a lithium ion
3. helium
4. hydrogen
5. beryllium
6. boron
7. oxygen
A 12,000 year-old sample of old carbon is 1/4 as radioactive as a current sample of carbon. Based on this value, what is the approximate half-life of Carbon 14.
1. 12,000 years
2. 12,000 days
3. 6,000 years
4. 6,000 days
5. 3,000 years
6. 3,000 days
7. 24,000 years
8. 48,000 years

	Look at this series: 58, 52, 46, 40, 34, ... What number should come next?
	A 26 B 28 C 30 D 32

Tuesday, February 11, 2014