Note:  There may be some questions on this exam that cover material that we did not discuss in class and that is not covered in your reading.   You do not need to worry about those questions. 

1. When a wave travels from one place to another, what is NOT transported?

a. energy
b. momentum
c. mass
d None of the above.

2. A crest of a periodic wave passes a reference point. A certain amount of time later, a second crest passes the same reference point. The amount of time that elapsed is called the __________ , and its reciprocal is called the __________ .

a. wavelength, frequency
b. frequency, period
c. period, wavelength
d. period, frequency
e. None of the above.

3. Two waves of the same frequency have different speeds. Which has the higher wavelength? The one with

a. the higher speed.
b. the lower speed.
c. the smaller amplitude.
d. the larger amplitude.
e. None of the above.

4. A radio wave has a wavelength of 11 meters and a speed of 3x108 meters/sec. What is the approximate frequency of the wave?

a. 33x108 Hz.
b. 37x10-6 Hz.
c. 27x106 Hz.
d. Radio waves don’t have frequencies that can be expressed in Hz, so the question makes no sense.

11. Which of the following is a conductor?

a. plastic
b. human body
c. silk
d. amber
e. None - all of the above are insulators.

12. When silk is used to charge a ______ rod (by rubbing), the rod contains a net positive charge and the silk a net ______ charge.
a. copper, neutral
b. amber, negative
c. amber, neutral
d. amber positive
e. glass, negative
f. glass, not enough information to solve

13. Which of the following objects is attracted by a negatively charged rod?

a. only other negatively charged objects.
b. only positively charged objects.
c. both positively charged and neutral objects.
d. only neutral objects.
e. Not enough information to predict correctly.

14. Two identical electroscopes, one initially charged and the other uncharged, are connected by a thin rod. If the foils on the electroscopes do not move, we can say that the connecting rod is

a. a conductor.
b. an insulator.
c. a semiconductor.
d. of the same, but opposite charge.

15. Suppose that you find an electroscope with separated foils. When you bring a positively charged rod near the electroscope, the foils move closer together. You can conclude that the electroscope is

a. uncharged.
b. positively charged.
c. negatively charged.
d. It is impossible to tell from such limited information.

16. Two charged objects are very, very far away from any other charges. If the distance between the charges is halved, the force between the charges

a. doubles.
b. gets reflected.
c. quadruples.
d. becomes one one-fourth as large.
e. is reversed in direction.
f. None of the above.

17. The electric force on a positive charge located near an isolated positive charge

a. points away from the isolated charge.
b. points toward the isolated charge.
c. is tangent to a circle centered on the isolated charge.
d. is zero.
e. None of the above.

18. The electric charge on an electron _____ that on a proton.

a. is identical to.
b. is smaller than (since the electron is less massive)
c. is the same size, but opposite in sign to
d. is larger than
e. None of the above.

19. Even though the electrical force is very much stronger than the gravitational force, gravity determines the motion of the heavens because

a. gravity sucks - i.e. it attracts all other masses.
b. the electrical forces have a longer range than gravity.
c. most objects are approximately electrically neutral.
d. (a) and (c) above.
e. None of the above.

20. The force that holds an atom together is

a. understood only by Buddhist monks.
b. well studied by chemists, but unknown to physicists.
c. magnetic.
d. nuclear.
e. electrical.
f. super-glue.
g. none of the above.

21. The lines of force drawn for an electric charge

a. point away from positive charges and toward negative charges.
b. point away from negative charges and toward positive charges.
c. never cross
d. (a) and (c) above are both true.
e. (b) and (c) above are both true.

22. What is the size of the electric force between a 3 C charge and a 4 C charge that are separated by 5 m?

a. k (3 C + 4 C) / (5 m)
b. k (3 C) (4 C) / (5 m)
c. k (3 C) (4 C) / (5 m)2
d. k (3 C + 4 C) / (5 m)2
e. None of the above.

24. Explain how an object (such as an electroscope) can be charged by induction.

26. What is the necessary condition for constructive interference to occur between two coherent waves (in two or three dimensions).

27. The superposition principle is a very powerful concept. Briefly discuss this idea, giving especial attention to the usefulness in predicting how wave interfere.

 

29. Explain HOW the balloon was made to stick to the wall during the demonstration.

31. Sketch the wave that results from the two waves shown in the figures below interfering with each other.

wpe9B.jpg (6621 bytes)

 

32. Sketch the reflection of the pulse wave for the case shown below. (2 points)

 

wpe9A.jpg (4367 bytes)

 

 

1. A gas can be identified by means of its spectral lines because each element

2. Cathode rays are

3. In his famous oil drop experiment, Millikan discovered that

 4. What force is responsible for holding the electrons in their orbits about nuclei?

 

5. Rutherford’s model of the atom as a very tiny, massive nucleus with the electrons orbiting could NOT explain why

6. As the temperature of a radiating object increases, the wavelength with the maximum intensity

7. According to Planck, the energy of a quanta can be calculated by

8. Photoelectrons are emitted from a metallic surface only when the incident light has more than a certain minimum

9. A clean surface of potassium metal will emit electrons when exposed to blue light. If the intensity of the blue light is increased, the _________ of the ejected electrons will also increase.

10. Bohr gave the following reason for the electrons in the hydrogen atom existing only in certain discrete energy levels

11. Which of the following is quantized in the Bohr atom?

12. An electron in the ground state (n=1) of the Bohr atom has a radius of 0.053 nm. What is the radius of the next larger orbit?

13. Two hydrogen atoms have electrons in the n = 3 energy level. The first electron jumps to the n = 2 level and the other jumps to the n = 1 level. Which property is larger for the first photon? Note: this problem requires significant thought

 14. Bohr could never explain why an electron was limited to certain orbits. De Broglie explained this by showing that electrons

15. The wave behavior of bowling balls is not observed because

 

16. If the two-slit experiment is performed with a beam of electrons so weak that only one electron passes through the apparatus at a time, what kind of pattern would you expect to obtain on the viewing screen (after a long period of time)?

 

17. If an electron is confined to a box and it has the lowest possible energy, where would you most likely find the electron?

18. According to Heisenberg’s uncertainty principle, it is impossible to precisely determine an object’s position and its _______ at the same time.

19. If you could determine which slit the electron goes through, what effect would it have on the two-slit interference pattern?

20. If radium (which is radioactive) and chlorine (which is not radioactive) combine to form radium chloride, the compound is

21. Three of the names below refer to the same thing. Which name does NOT?

22. The atomic mass of a nucleus is approximately given by the number of its

23. Atoms whose nuclei contain the same number of protons but different number of neutrons are called

24. What is the daughter formed when 146C decays by beta decay?

25. If a nucleus decays by emitting an alpha particle, the daughter has

26. A radioactive material has a half-life of 2 minutes. If you begin with 512,000 radioactive nuclei, approximately how many would you expect to have after 4 minutes?

27. Which of the following is a unit that reflects the biological effect caused by radiation?

28. Which of the forces is responsible for holding the nucleons together to form the nucleus?

 

30. Briefly discuss the phenomena of blackbody radiation OR the photoelectric effect. Describe the phenomena, how classical physics failed, and how quantum physics provided an explanation. (6 pts)

 

31. In Quantum Mechanics, massive particles are represented as waves (at least mathematically).

32. Assume that you have two nuclei that have a half-life of 10 minutes. One has just been created as the daughter of a decay, while the other has already been in existence for 19 minutes. Which is more likely to decay in the next minute? Justify your answer! (4 pts)

 33. Why did some philosophers find the Heisenberg Uncertainty Principle very disturbing? ( 6 pts)

 34. You are given 3 radioactive cookies: one emits alpha, one beta and the third gamma. You must eat one, hold one and put one in your pocket. Explain what ( and why) you would do with each cookie to minimize harm to yourself. (6 pts)

35. For a given metal, the spectrum of intensity versus wavelength for x-rays can be loosely described as a blunt nosed whale, facing left, that has spikes on its back. Explain how each part of this spectrum arises. (6 pts)

36. Discuss the dual nature of the quantum physical world. Sometimes a wave description is appropriate and other times it is not. How does nature cope with the dual aspects of its most elementary inhabitants? (6 points)

 

 

 

 

 

 

38. Refer to the figure above.   a) Where would you expect to be the most likely location of ‘finding’ the particle? Why?

  b) Where would you think is the least likely position for finding the particle? Why?