Physics Exam Number 2

17. What is the universe mostly made of?

*A. Dark energy

11. Planck's constant is about 7 x 10-34, in metric units. Suppose that Planck's constant were larger than it is actually is. Which of the following would then occur?

*A. Individual photons would have larger energies, making it easier to observe individual photons

8. What happens to an electron's wave packet if an accurate velocity measurement is performed?

*A. It suddenly changes to a new wave packet having a very small uncertainty in velocity, but a large uncertainty in position.

What happens to a particle's wave packet when a highly accurate position measurement is performed?

*A. It suddenly makes a transition into a state of smaller uncertainty in position and greater uncertainty in velocity.

8. Who discovered that radiation is quantized?

*A. Max Planck

The post-Newtonian age began in 1900 when

*A. Max Planck introduced the quantum of energy.

9. Which of the following provides evidence for the quantization of light?

*A. The individual dots seen on a photographic plate when a photo is taken at extremely short exposure times

3. A photon is

*A. a particle-like quantum of radiation.

1. According to Heisenberg's uncertainty principle, electrons are more unpredictable than protons. This is because electrons

*A. have a smaller mass.

6. When we say that an electromagnetic field is "quantized," we mean that it

*A. is allowed to have only certain particular values of total energy.

17. One experimental observation that demonstrates Einstein's ideas on the relativity of time, is

*A. muons "live" longer when moving rapidly than they do when they are at rest.

19. In the double-slit experiment, the entire matter field or EM field instantaneously collapses to the single interaction point when the field interacts with the screen. This is an example of

*A. quantum nonlocality.

18. Werner Heisenberg and Niels Bohr believed that

*A. quantum theory is correct and leads us to a new view of "reality" at the microscopic level.

20. According to the theory of cosmic inflation, the large-scale clumping of matter (into stars, galaxies, etc.) that we observe in the universe had its origin in

*A. quantum uncertainties that were then stretched by the expansion of the universe.

1. The two main theories of 20th century physics are

*A. relativity and quantum theory.

11. The basic difference between the special and general theories of relativity is that

*A. the first deals with nonaccelerated observers and the second deals with accelerated observers.

12. Nineteenth-century scientists thought the "ether" to be

*A. the medium for the propagation of light waves.

3. One experiment that informs us that gravity bends lightbeams is

*A. the observed bending of light from stars as the light passes the sun.

22. Suppose that a certain atom had just 4 different energy levels. How many different frequencies could be emitted by this atom?

*B. 6

12. How do we know the shape of the universe?

*B. By observation of the angular size of a typical wavelike disturbance in the cosmic microwave background.

27. What feature of Einstein's theory of relativity is demonstrated by the phenomenon of matter-antimatter annihilation?

*B. E = mc2.

10. Which of the following provides evidence that light is made of waves?

*B. Interference effects seen when light passes through a narrow opening

21. You are in a spaceship moving past Earth at nearly lightspeed and you observe Mort, who is on Earth. You measure his mass, pulse rate, and size. How are they different from the values measured by Mort himself?

*B. Mass has increased, pulse rate has slowed down, and size is reduced along the direction of motion.

9. According to the theory of relativity, is everything relative?

*B. No, lightspeed is not relative.

11. Which of the following experiments demonstrates the fact that the mere act of observation, or detection, causes changes in the microscopic world?

*B. The electron double-slit experiment with a detector placed behind one of the slits

16. Which of the following is a feature of quantum physics but not a feature of Newtonian physics?

*B. The observation process must be included as part of the theory.

17. How does quantum uncertainty differ form the uncertainty involved in a coin flip?

*B. With sufficient information, a coin flip's outcome can be predicted, but no amount of information can remove quantum uncertainties.

24. Velma, who is moving past you at a high rate of speed, holds a meter stick and a standard kilogram. Is it possible that your measurements could show the standard kilogram to have a mass of 2 kg while the meter stick still has its normal length of 1 m?

*B. Yes, if Velma holds the meter stick perpendicular to its direction of motion.

15. One similarity between electrons and photons is

*B. both are the quanta of a field.

13. The double-slit experiment with electrons illustrates the surprising idea that

*B. electrons sometimes behave like waves.

4. According to the principle of relativity, an observer who has no communication with the world outside of her laboratory will be unable to detect

*B. her laboratory's velocity

3. If a microscopic particle's uncertainty in velocity is reduced,

*B. its uncertainty in position must increase enough to satisfy the uncertainty principle.

26. A conclusion that follows from E=mc2 is that, at the microscopic level,

*B. matter is made of force fields.

14. The electron microscope is based on the use of

*B. matter waves.

10. In a closed universe, the angles of a triangle add up to

*B. more than 180 degrees.

A certain type of atom has only four energy levels, as shown in the figure. The "spectral lines" produced by this element are all visible, except for one ultra-violet line. The quantum jump that produces the UV line is

*B. state 4 to 1.

4. According to Einstein, gravity is

*B. the bending of space that is caused by masses.

19. The standard "picture" of the hydrogen atom as a tiny proton with an electron moving in an ellipse around it is extremely oversimplified. The main thing wrong with this picture is

*B. the electron should be pictured as a spread-out matter field.

7. Mort stands on Earth. Velma moves away from him in a rocket, at 299,000 km/s (1000 km/s slower than lightspeed). Mort sends a laser beam toward Velma. As the tip of the beam passes her rocket, Velma observes that

*B. the laser beam moves past her at 300,000 km/s.

7. The cosmic microwave background is

*B. the now-cooled radiation that was released by the big bang.

3. "Unless you look outside, you cannot tell how fast you are going." This is one way of stating

*B. the principle of relativity

18. Velma passes Mort at a speed of 0.75c. At this speed, the "time dilation factor" is 1.5. In other words, Mort observes a 1-second tick of Velma's clock to take 1.5 seconds. Suppose that they are born at the same time, and that Mort observes himself to live 30 years. As Mort dies, how old will he observe Velma to be?

*C. 20 years

23. As evidence for the cosmic inflation hypothesis, this hypothesis explains

*C. Both of these (A. the origin of the "clumping" of matter and energy that we see today in such aggregations as stars and galaxies. B. the observed "flatness" of the overall three-dimensional universe. )

6. Mort stands on Earth. Velma moves away from him in a rocket, at 299,000 km/s (1000 km/s slower than lightspeed). Mort sends a laser beam toward Velma. As the tip of the beam passes her rocket, Mort observes

*C. Both of these.

25. The difference between the "ground state" and an "excited state" for a hydrogen atom is

*C. Both of these. (A. the excited state has more energy. B. the atom can radiate when it is in an excited state, but not when it is in a ground state.)

14. According to quantum theory,

*C. Both of these. (A. nature is "non-local," i.e., instantaneously connected across a distance. B. individual microscopic events are inherently unpredictable. )

8. The big bang created

*C. Both of these. (matter, energy, space, time)

2. Velma, inside a train moving at 20 m/s, throws a rock in the forward direction at 5 m/s. According to her the rock moves at 5 m/s. According to Mort, standing on Earth outside the train, the rock moves at [approximately] 25 m/s. Who is correct?

*C. Both, relative to their own reference frames.

28. You separate two magnets that are initially held together by magnetic forces. How does this affect the mass and energy of the system of magnets?

*C. It creates additional mass, located in the space between the two magnets, and also additional energy

25. Can a rock be accelerated up to lightspeed?

*C. No, because any material object's mass becomes infinite as the object approaches lightspeed.

10. In the "special theory of relativity," what does the word "special" refer to?

*C. This theory is restricted to the observations of non-accelerated observers.

21. Can anything go faster than light?

*C. Yes, space can expand at faster then lightspeed.

4. During the double-slit experiment with light, the region between the slits and the screen contains

*C. an electromagnetic field.

8. Continuing the preceding two questions, whose observations are really correct?

*C. both (mort and verma)

6. Which one has the smallest range of possibilities [or quantum uncertainty range]?

*C. dust grain

24. When an atom undergoes a "quantum jump" into a lower-energy state, the atom

*C. emits a photon

13. According to Bell's nonlocality principle,

*C. entangled particles exhibit correlations that are explainable only by real, instantaneous connections between them.

18. According to the theory of cosmic inflation, during a brief early "inflationary period," the universe

*C. expanded at a speed that exceeded lightspeed.

1. According to the principle of equivalence, acceleration is equivalent to

*C. gravity.

5. Higher energy photons have

*C. higher frequency.

9. In an open universe, the angles of a triangle add up to

*C. less than 180 degrees.

15. Velma zooms past Mort at half of lightspeed. Mort observes Velma's clock. He observes that her clock runs

*C. slow.

16. Velma zooms past Mort at half of lightspeed. Velma observes Mort's clock to run

*C. slow.

12. In the double-slit experiment with light,

*C. the impact point of each photon cannot be predicted, but the overall pattern can be predicted.

22. Material objects cannot be accelerated up to lightspeed because

*C. their inertia increases [toward infinity, i.e., without bound] as they approach lightspeed.

7. Which of the following colors has the most energy per photon?

*C. violet

6. The big bang is thought to have occurred about

*D. 14 billion years ago.

Which of the following is a consequence of Heisenberg's uncertainty principle?

*D. All of these. (A. The fact that atoms don't collapse. B. The unpredictability of radioactive decay. C. The uncertainties involved in determining a person's genetic inheritance when DNA molecules are combined. )

5. Which chemical elements were created during the first few minutes of the "big bang" that started our universe?

*D. Only the first three elements: hydrogen, helium, and lithium.

23. Mort is on Earth, and Velma passes him at a high speed. Mort and Velma each carry a standard kilogram. Concerning the kilograms, Mort observes that

*D. Velma's is more massive than 1 kilogram and Mort's has a mass of 1 kilogram.

14. The 1964 experiment that checked the validity of the principle of the constancy of lightspeed involved

*D. a fast-moving sub-atomic particle that emitted radiation both forward and backward.

2. In coming to the conclusion that lightbeams are bent by gravity, Einstein reasoned that

*D. accelerated observers would find that lightbeams bend, so gravity must also bend lightbeams.

7. Niels Bohr is known

*D. as the leading philosophical interpreter of quantum theory.

19. According to the theory of cosmic inflation, at what time in the history of the universe did inflation occur?

*D. at a tiny fraction of the first second, but not quite at the very beginning of the big bang

4. According to the uncertainty principle, a particle such as an electron

*D. does not have a precise position or a precise velocity.

15. One unusual aspect of dark matter is

*D. it does not interact with electromagnetic radiation.

13. Einstein believed that the principle of relativity should apply to Maxwell's theory of electromagnetism. Which basic principle or law did this lead Einstein to propose?

*D. the constancy of lightspeed

20. When we speak of the "spectrum" of a radiation source, we are referring to

*D. the set of frequencies that the source can emit.

12. In quantum theory, "entanglement" refers to

*D. two particles sharing a single quantum field (EM field or matter field) with each other.

15. Which quantum characteristic(s) would quantum computers exploit in order to achieve great computational power with only a few individual quantum elements or "qubits"?

*E. Both uncertainty and entanglement.

5. Which of the following is one way of stating the principle of relativity?

*E. No physical experiment, conducted entirely within your own lab, can tell you how fast you are moving relative to anything outside the lab.

10. If Planck's constant were smaller than it actually is, how would the uncertainty principle be affected?

*E. Quantum uncertainties would be smaller.

22. Cosmic inflation caused the universe to expand, for a brief period, at faster than lightspeed. But special relativity says that nothing can move faster than lightspeed. How can this contradiction be resolved?

*E. Special relativity says nothing can move through space at faster than lightspeed, but doesn't restrict the speed at which space can expand.

19. A certain star is 1000 light years from Earth. According to the theory of relativity, is it physically possible for Mort to travel from Earth to this star during Mort's normal lifetime?

*E. Yes, by traveling at nearly lightspeed.

16. Schroedinger discovered

*E. a way to predict the wave patterns seen in experiments involving matter waves.

23. When an atom emits radiation

*E. an electron makes a quantum jump from one quantum state to another.

16. Recent evidence from very distant supernova explosions indicates that the universe is expanding

*E. at an increasing rate.

2. Quantum theory was developed

*E. by Planck, Schroedinger, Einstein, and many other scientists.

5. Which one has the largest range of possibilities [or quantum uncertainty range]?

*E. electron

20. Velma passes Mort at a high speed. Each holds a meter stick, oriented parallel to the direction of relative motion. Mort observes that

*E. his meter stick is 1 m long, and Velma's meter stick is less than 1 m long.

20. In the context of the double-slit experiment, quantum uncertainty refers to

*E. our inability to precisely predict the point at which a spread-out matter field or EM field will interact with the screen.

2. In quantum theory, a "wave packet"

*E. represents one particle having a range of possible positions and a range of possible velocities.

11. The evidence favors a universe whose overall geometry is flat. That evidence comes from observations of

*E. the cosmic background radiation.

18. In the electron double-slit experiment, the Schroedinger equation enables scientists to predict

*E. the overall pattern made by a large number of electron impacts on the screen.

13. Galaxies seem to be made mostly of dark matter. One type of evidence for this comes from observations of

*E. the speeds at which gas clouds orbit the centers of galaxies.

14. The amount of dark matter in the universe is

C. many times more than the amount of visible matter.