# White light is spread out into spectral hues by a grating

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```					Physics 112

Exam 4

Summer 2006

Physics 112 Summer 2006 Exam 4 Thursday, August 3

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Physics 112

Exam 4

Summer 2006

61. Three identical charges of 3.0 μC are placed at the vertices of an equilateral triangle which measures 30 cm on a side. What is the magnitude of the electrostatic force which acts on any one of the charges? A) 1.6 N B) 1.8 N C) 2.0 N D) 2.2 N E) 2.4 N

62. A downward force is exerted on a negative charge. What is the direction of the electric field at the point where the charge is located? A) Left B) Right C) Upward D) Downward E) Not enough information to answer the question

63. The length of a wire is doubled and the radius is doubled. By what factor does the resistance change? A) four times as large B) twice as large C) half as large D) quarter as large E) the same

64. A heavy bus bar is 20 cm long and of rectangular cross-section, 1.0 cm × 2.0 cm. What is the voltage drop along its length when it carries 4000 A? (The resistivity of copper is 1.68 × 10-8 Ω∙m.) A) 3.00 V B) 1.20 V C) 0.67 V D) 0.34 V E) 0.067 V

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Physics 112

Exam 4

Summer 2006

65. When resistors are connected in series, A) the same power is dissipated in each one B) the potential difference across each is the same C) the current flowing in each is the same D) More than one of the given answers is true E) Non of the given answers is true 66. A battery with emf of 12 V and internal resistance 2 Ω is connected to the resistance of 22 Ω. What is the terminal voltage of the battery? A) 12 V B) 11 V C) 10 V D) 9 V E) 3 V

67. A 2.0-μF capacitor is charged to 12 V and then discharged through a 4.0 × 106 Ω resistor. How long will it take for the voltage across the capacitor to drop to 3.0 V? A) 3 s B) 5 s C) 8 s D) 11 s E) 22 s

68. An electron moves with a speed of 5.0×104m/s parallel to a uniform magnetic field of 0.20T. What is the magnitude of the magnetic force on the electron? A) 4.4 × 10-14 N B) 1.6 × 10-15 N C) 1.6 × 10-24 N D) 2.6 × 10-24 N E) zero

69. Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the same direction, A) one wire is lifted slightly as the other wire is forced against the table's surface. B) both wires are lifted slightly. C) the wires repel each other. D) the wires attract each other. E) there is no interaction between weirs
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Physics 112

Exam 4

Summer 2006

70. A long solenoid has 100 turns/cm and carries current 1.00A. A sphere of the radius 1.00 cm is placed inside the solenoid. Find the magnetic flux through the sphere. A) 1.6*10-6 T*m2 B) 1.6*10-7 T*m2 C) 4.0*10-8 T*m2 D) 8.0*10-8 T*m2 E) zero

71. A coil of 160 turns and area 0.20 m2 is placed with its axis parallel to a magnetic field of 0.40 T. The magnetic field changes from 0.40 T in the x-direction to 0.40 T in the negative xdirection in 2.0 s. If the resistance of the coil is 16 Ω, at what rate is power generated in the coil? A) 5.0 W B) 10 W C) 15 W D) 20 W E) 25 W

72. Electromagnetic waves are A) longitudinal B) transverse C) both longitudinal and transverse D) neither longitudinal or transverse E) electric field oscillations longitudinal, but magnetic are transverse

73. Light enters a substance from air at 30.0° to the normal. It continues through the substance at 23.0° to the normal. What would be the critical angle for this substance? A) 51.4° B) 45.0° C) 36.7° D) 12.6° E) 10.1°

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Physics 112

Exam 4

Summer 2006

74. A person's face is 30 cm in front of a concave shaving mirror. If the image is an erect image 1.5 times as large as the object, what is the mirror's focal length? A) 20 cm B) 50 cm C) 70 cm D) 80 cm E) 90 cm

75. The separation between adjacent maxima in a double-slit interference pattern using monochromatic light is A) greatest for red light. B) greatest for green light. C) greatest for blue light. D) the same for all colors of light. E) it is smallest for green light

76. White light is spread out into spectral hues by a grating. If the grating has 2000 lines per centimeter, at what angle will red light (640 nm) appear in the first order? A) 3.57° B) 7.35° C) 11.2° D) 13.4° E) 15.2°

77. An important reason for using a very large diameter objective in an astronomical telescope is A) to increase the magnification. B) to increase the resolution. C) to form a virtual image, which is easier to look at. D) to increase the width of the field of view. E) to increase the depth of the field of view.

78. When light of wavelength 350 nm is incident on a metal surface, the stopping potential of the photoelectrons is 0.500 eV. What is the work function of the metal? A) 0.500 eV B) 1.24 eV C) 2.48 eV D) 3.04 eV E) 3.54 eV

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Physics 112

Exam 4

Summer 2006

79. An electron is accelerated through a potential difference of 150 V. What is its wavelength? A) 0.1 nm B) 1 nm C) 1 mm D) 1 cm E) 10 cm

80. What is the energy difference between the second excited state and first excited state of an electron in the “box” of size L=1nm? A) 1.9 eV B) 1.1 eV C) 0.6 eV D) 0.3 eV E) 0.2 eV

81. A neutral atom has an electron configuration of 1s22s22p63s23p2. What is its atomic number? A) 5 B) 11 C) 14 D) 20 E) 22

82. Compared to the masses of its separate protons and neutrons, the total mass of a stable nucleus is always A) less B) the same C) greater D) zero E) it depends from the atomic number

83. A radioactive sample has a half-life of 10 min. What fraction of the sample is left after 40 min? A) 1/2 B) 1/4 C) 1/8 D) 1/16 E) 1/32

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Physics 112

Exam 4

Summer 2006

84. In the fission reaction 235U + 1n → 141Ba + 92Kr + neutrons, the number of neutrons produced is A) zero. B) 1 C) 2 D) 3 E) 4

85. What is the Q value for the following reaction? 7Li 1p 4He + 4He + = (7.016005) (1.007825) (4.002603) (4.002603) A) 13.57 MeV B) 15.37 MeV C) 17.35 MeV D) 18.53 MeV E) 19.24 MeV

86. What is the wavelength of 7.0-TeV protons? A) 550 nm B) 750 nm C) 5.4x10-15 m D) 3.2x10-18 m E) 1.8x10-19 m

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Physics 112

Exam 4

Summer 2006

Scratch Paper (intentionally left blank).

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Physics 112

Exam 4

Summer 2006

Record Sheet
You may fill in this sheet with your choices, detach it and take it with you after the exam for comparison with the posted answers 61 71 81

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