Final Exam---QUIZ 10

1 The source of all magnetism is

a. tiny pieces of iron

b. the force of gravity

c. electric charge in motion

d. nota

2 True of False. A current in a conducting wire does  produce a magnetic field. 

a. True

b. False

3 A conducting long straight wire  loop lies vertically in the plane of the page. A current flows upward through the wire. What is the direction of the magnetic field directly to the right of the wire?  (It would help if you sketched  the vertical straight line and drew an arrow pointing up on the line representing the current.  Hint:  Use the right hand rule for long straight wires by pointing your right thumb upward  in the direction of the current. Your right fingers will  point in the direction of the  magnetic field on the right of  the line.) 

a. in 

b. out

c. nota 

4 True or False.  A magnetic field does not exert a  force on a charge in motion.

a. True

b. False

5  True or False.  The magnetic force on a charge moving in a magnetic field  is   perpendicular to the velocity of the  particle.   

a. True

b. False

6. True or False.  The magnetic force on a  charge moving in a magnetic field  is  perpendicular to the magnetic field. 

a. True

b. False

7  True or False.  The magnetic force on a straight,  current carrying wire in an external magnetic field  is not  perpendicular to the current.   

a. True

b. False

8 True or False.  The magnetic force on a straight,  current carrying wire in an external magnetic field  is not perpendicular to the magnetic field.   

a. True

b. False

9  2 long straight wires are  parallel and their currents flow in the same  direction. The two wires

a. attract each other

b. repel each other

10 True or False. The geographic south  pole  of the Earth coincides with the Earth's   magnetic north pole.

a. True

b. False

11. True or False. Magnetic field lines come out of the south pole  and enter the north  pole of a magnet.  

a. True

b. False 

12.True or False. A length of wire is bent into a  closed loop and a magnet near the loop is moving relative to loop. The current in the loop is zero. 

a. True

b. False

13. True  or False. A length of wire is bent into a  closed loop and a magnet within the loop is pulled (moved) away from the loop. The current in the loop will be zero.

a. True

b. False

14. A circular loop of copper wire is lying flat  on a horizontal table. A bar magnet is held with its North pole downward vertically above the center of the coil. The magnet is released from rest and falls toward the coil. As viewed from above, as it falls,  the magnet induces 

a.  a counter-clockwise current in the loop 

b. a clockwise current in the loop

15. According to Faraday's Law, a current flows in a loop of wire  when there is a change in

a. the electric field intensity through  the loop.

b. the magnetic field intensity through the loop.

16. A device that transforms mechanical energy into electrical  energy is a 

a. generator

b. motor

c. transformer

d. nota

17.  A device that transforms electrical energy into mechanical  energy is a 

a. generator

b. motor

c. transformer

d. nota

18. A big Neon sign requires about 12,000 volts (output voltage) to operate. The "step up"  transformer circuit uses a 120-Volt (input voltage) source.  What is the ratio of primary to secondary turns on the transformer?

a. 1/100  b. 100/1  c.  200/1 d. nota

19. True or False. Most of the waves in the electromagnetic spectrum are visible to the naked eye. 

a. True

b. False

20. The main difference between  ganma-ray waves and  micro-waves in a vacuum is the 

a. wave speed

b. wavelength

21. Which of these waves has the  largest frequency?

a. yellow light  waves

b. infrared waves

c. X-Rays

d. ultraviolet waves

22. Which of these waves has the shortest wavelength?

a. infra-red  waves

b. radio waves

c. visible yellow  light

d. micro-waves

23. Which does  not require a physical medium in which to travel?

a. x-ray  waves   b. sound waves

24.  The natural frequency of vibrating electrons in atoms of glass is in the 

a. infrared part of the spectrum

b. visible part of the spectrum

c. microwave  part of the spectrum

d. nota

25. The speed of light in  water is 

a. more than its speed in a vacuum

b. less than its speed in a vacuum

c. the same as its speed in a vacuum

26.  Compared to  its speed in a vacuum, the average speed of a beam of light in glass  is 

a. more

b. less

c. the same

35.  A double slit arrangement causes interference fringes for yellow light. To produce narrower–spaced  slits, what type of light should be used ?

(a) red light (b)  blue light  (c) nota

36. If the path length difference between two identical and coherent beams is two wavelengths when they arrive at the screen, they produce a (a)  dark spot  (b) light spot.

37.  When the reflected path from one surface of a thin film is one full wavelength different in length from the reflected path from the other surface and no phase change occurs, the result will be
(a) constructive interference (b) destructive interference

38. When the reflected path from one surface of a thin film is one -half wavelength different in length from the reflected path from the other surface and no phase change occurs, the result will be
(a) constructive interference (b) destructive interference

39.  What percentage of light is transmitted by two ideal Polaroids one on top of the other with their polarization axes aligned?

(a)  0  %    (b)  100 %   (c) nota

40.  What percentage of light is transmitted by two ideal Polaroids one on top of the other with their polarization axes at right angles to each other?

(a)  0  %    (b)  100 %   (c) nota

41. Why is a gamma ray photon more energetic than an X-ray photon?
(a) because it has a larger speed (b) because it has a larger wavelength (c) because it has a larger frequency  (d) nota

42. Green light is emitted when electrons in a substance make a particular energy – level transition. If blue light were emitted instead from the same substance, the light would correspond
(a) a greater change of  energy in the atom (b) a lesser change of energy in the atom (c) nota

43. If we double the  wavelength  of electromagnetic radiation, what happens to the energy of its photons?
(a) doubles  (b) reduced by a factor of one-half  (c) does not change

44. Which has the greatest energy,  a photon of (a) visible light (b) infrared radiation (c) ultra-violet radiation ? 

45. Fluorescent materials are  noteworthy because they are excited by ultraviolet radiation and upon de-excitation emit (a) gamma radiation (b) visible light (c) x-rays  (d) nota

46. The frequency of a violet photon is about twice that of red light. How does the energy E of a violet photon compare with the energy of a red photon?

a. The energy is twice  the energy  of a red photon

b. The energy is one half the energy of a red photon

c. same energy

47. The photoelectric effect best illustrates the 

a. wave nature of matter

b. particle nature of light

c. wave nature of light

d. nota

48. In the photoelectric effect, the higher the frequency of  the illuminating light on the photosensitive surface, the greater the

a. number of ejected electrons

b. kinetic energy of ejected electrons

c. nota

49.  Does the DeBroglie wavelength  of an electron become longer or shorter as the momentum increases ? a. longer b. shorter c. remains the same

50.  Which of the following is evidence of the wave nature of electrons?
(a) the photoelectric effect
(b) the interference pattern on a screen when a beam of electrons  is directed through double slits.

51. One electron travels twice as fast as another. Which has the longer wavelength?  (a) faster electron (b) slower electron (c) wavelengths are the same

52.  A hydrogen atom and a uranium atom move  at the same speed. Which has the largest wavelength?
(a) hydrogen atom  (b) uranium atom (c) nota

53. In the photo–electric effect which determines the kinetic energy of the ejected electrons ? (a) the brightness of the incident light (b) the frequency of the incident light (c) nota

54. In the photo–electric effect which determines the number of  ejected electrons ? (a) the brightness of the incident light (b) the frequency of the incident light (c) nota

55. What convinced Rutherford that the gold foil was mostly empty  space?  (a) finding most alpha particles were un-deflected (b) finding some alpha particles bounced backwards

56. What convinced Rutherford that the particles of the gold foil in empty  space were massive?  (a) finding most alpha particles were un-deflected (b) finding some alpha particles bounced backwards

57. If the electron in a hydrogen atom obeyed classical mechanics instead of quantum mechanics,  what kind of spectrum would it emit ? (a) a continuous spectrum (b) a line spectrum

58. In terms of wavelength de Broglie said that  the smallest orbit that an electron can have about the hydrogen nucleus is (a) one wavelength

(b) two wavelengths (c) three wavelengths (d) one-half a wavelength (e) nota

59. What is the maximum number of paths for de-excitation available to a hydrogen atom excited to level 3 (n = 3) in changing to the ground state (n = 1) ?  (a) one  path (b) two paths  (c) three paths (d) nota

60. What type of radiation---alpha, beta, or gamma--- produces the greatest change in atomic number?  (a) alpha (b) beta (c) gamma

61. True or False. It is possible for a   common hydrogen nucleus to emit an alpha particle  (a) True (b) False

62. X-rays are  most similar to  which of the following?  (a) alpha rays
(b) beta rays (c) gamma rays

63.  What do all isotopes have in common?  (a) same number of protons
(b) same number of neutrons

64. Which force  tends to hold particles in an atomic nucleus  together? (a) strong force (b) electric force 

65. Radiation from a point source obeys the inverse square law.

 If a Geiger  counter 1 m from a small sample registers 360 counts per minute, what will be the count rate (in counts per minute)  3m   from the source ? (a) 180  (b) 90   (c) 40 (d) nota

66. When

emits an alpha particle, it transforms to a different element.  What’s the atomic mass number of the new element? (a) 213 (b) 214
(c ) 215 (d)  222 (e) nota

67. In the previous problem what is the  atomic number  of the new  element? (a) 80  (b) 86 (c) 82 (d) nota

68. If a sample of radioactive isotopes has a half life of 1 day, how much of the original sample is left at the end of the second day?
(a) one –half (b) one quarter (c) one-eighth

69. Most of today’s nuclear power plants use (a) fusion (b) fission

70. In fission the combined mass of the fission products is (a) less than the mass of the original uranium nucleus (b) more than the mass of the original uranium nucleus

71. In a nuclear fusion reaction , which has more mass, the initial hydrogen isotopes or its products ? (a) initial hydrogen isotopes
 (b) products

72. Chain reactions in a fission reactor are caused by (a) kinetic energy (b) energy conversion (c) mass conversion (d) ejected neutrons

73. A common nuclear power reactor (a)  heats water (b) generates electricity directly  (c) gets energy from nothing

74. In both fission and fusion, energy is released while mass (a) decreases (b) remains unchanged; is conserved (c) increases (d) may increase or decrease

75. In either a fission or fusion event, a quantity that remains unchanged is (a) kinetic energy (b) mass (c) number of nucleons (d) binding of nucleons