p117b_07_t4_ans - 1) A ) x 1014 Hz electromagnetic wave...

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Unformatted text preview: 1) A ) x 1014 Hz electromagnetic wave propagates in carbon tetrachloride with a speed of 2.05 x 108 m/s. The wavelength of the wave in carbon tetrachloride is closest to: A) ) nm B) ) nm C) ) nm D) ) nm E) ) nm Answer: A 2) A planar electromagnetic wave is propagating in the positive x-direction. At a certain point P and at a given instant, the electric field of the wave is given by E = -j ) mV/m. The magnetic vector of the wave, at the point P at that instant is closest to ( i,j,k are unit vectors along +X,+Y and +Z axes): ) -¯– ¶ ª A) ) -¯– ¶ ª, ) -–¯ ¶ ª B) ) -–¯ ¶ ª, C) ) -–¯ ¶ ª, D) ) -¯– ¶ ª, E) ) -– ¯ ¶ ª, Answer: A ) -–¯ ¶ ª ) -¯– ¶ ª ) -– ¯ ¶ ª 3) The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of ) mW/m 2. The wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. The total energy that traverses the area in a time interval of one minute is closest to: A) ) J B) ) J C) ) J D) ) J E) ) J Answer: A 4) An 800 kHz radio signal is detected at a point ) km distant from a transmitter tower. The electric field amplitude of the signal at that point is ) mV/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The magnetic field amplitude of the signal at that point, in nT, is closest to: A) ) B) ) C) ) D) ) E) ) Answer: A 5) A radiometer has two square vanes (1 cm by 1 cm), attached to a light horizontal cross arm, and pivoted about a vertical axis through the center. The center of each vane is 6 cm from the axis. One vane is silvered and it reflects all radiant energy incident upon it. The other vane is blackened and it absorbs all incident radiant energy. Radiant energy, which has an intensity of 300 W/ m2, is incident normally upon the vanes. In the figure above, the radiation pressure on the blackened vane is closest to: A) 1 x 10 -10 B) 1 x 10 -9 C) 1 x 10 -8 D) 1 x 10 -7 E) 1 x 10 -6 Answer: E 6) An electromagnetic wave polarized parallel to the z-axis is traveling in the positive direction along the x-axis. How can this wave best be detected using a straight wire antenna? A) Orient the antenna parallel to the x-axis. B) Orient the antenna parallel to the y-axis. C) Orient the antenna parallel to the z-axis. D) The antenna will work equally well for any of these orientations. E) This wave cannot be detected with a straight wire antenna. A loop antenna must be used. Answer: C 7) A ray in air is incident on a glass plate whose index of refraction is ) . The angle of refraction is one half the angle of reflection. The angle of refraction is closest to (in degrees): A) ) B) ) C) ) D) ) E) ) Answer: A FIGURE 8) A ray in glass arrives at the glass-water interface at an angle of 48 degrees with the normal. The refracted ray, in water, makes a ) degree angle with the normal. The index of refraction of water is 1.33. In the above figure, the angle of incidence of a different ray in the glass is ) degrees. The angle of refraction in the water is closest to (in degrees): A) ) B) ) C) ) D) ) E) ) Answer: B 9) When light travels from air into water, A) its velocity, wavelength and frequency all change. B) its velocity changes, but its frequency and wavelength do not change. C) its frequency changes, but its velocity and wavelength do not change. D) its velocity and wavelength change, but its frequency does not change. E) its wavelength changes, but its velocity and frequency do not change. Answer: D FIGURE 10) As shown in the figure above, in the investigation of a new type of optical fiber (index of refraction n = ) ), a laser beam is incident on the flat end of a straight fiber in air. What is the maximum angle of incidence θ (in degrees) if the beam is not to escape from the fiber? A) ) B) ) C) ) D) ) E) ) Answer: A 11) The following are positioned in sequence: A source of a beam of natural light of intensity I ; three ideal polarizers A, B, and C; and an observer. Polarizer axis angles are measured clockwise from the vertical, from the perspective of the observer. The axis angle of polarizer A is set at zero degrees (vertical), and the axis angle of polarizer C is set at 50 degrees. ƒ?¹ ª , ƒ? ¹ ª , šm ` €ó¸ ª , Ð ÉŽ F ƒ¾ V Ñ , p ËŽ A) 40 and 90 B) 40 and 130 C) 40 and 140 D) 90 and 130 E) 90 and 140 Answer: E 12) As you walk away from a plane mirror on a wall, your image A) gets smaller. B) may or may not get smaller, depending on where the observer is positioned. C) is always a real image, no matter how far you are from the mirror. D) changes from being a virtual image to a real image as you pass the focal point. E) is always the same size. Answer: E 13) An erect object is 50 cm from a concave mirror of radius 60 cm. The character of the image is: A) real and erect B) real and inverted C) virtual and erect D) virtual and inverted E) indeterminate Answer: B 14) Suppose you wanted to start a fire using sunlight and a mirror. Which of the following statements is most accurate? A) It would be best to use a plane mirror. B) It would be best to use a convex mirror. C) It would be best to use a concave mirror, with the object to be ignited positioned at the center of curvature of the mirror. D) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature. E) One cannot start a fire using a mirror, since mirrors form only virtual images. Answer: D 15) In the figure above, a convex lens of focal length +150 cm is 90 cm to the right of a concave lens. A point source of paraxial rays is at P, 72 cm to the left of the concave lens. This point source produces a parallel beam to the right of the convex lens. The focal length of the concave lens, in cm, is closest to: A) -33 B) -43 C) -60 D) -100 E) -360 Answer: E 1) A 2) A 3) A 4) A 5) E 6) C 7) A 8) B 9) D 10) A 11) E 12) E 13) B 14) D 15) E ...
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This document was uploaded on 09/05/2011.

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