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Physics 112 Exam 3 Summer 2012 Name_________________ Physics 112 Summer 2012 Exam 3 Monday, July 23 Directions: This 60-minute exam consists of twenty multiple-choice questions. This test is worth 20% of your final grade. (One point is equal to 1% of the final grade.) The questions on this test are not in order of difficulty. You must mark all of your answers on both your test and answer sheet. In marking the multiple choice bubble sheet use a number 2 pencil. Do not use ink. If you did not bring a pencil, ask for one. Fill in the appropriate circles completely. If you need to change any entry, you must completely erase your previous entry. Carefully read each question and its five possible answers. Select one and only one answer for each question. Choose the answer that is closest to the correct one. When you are finished with the exam, return the bubble sheet and the exam itself. Good luck! Page 1 of 7 Physics 112 Exam 3 Summer 2012 41. A light beam coming from an underwater spotlight exits the water (index of refraction is n=1.33) at an angle of 66.0° to the vertical. At what angle of incidence does it hit the air–water interface from below the surface? A) B) C) D) E) 33◦ 43◦ 53◦ 63◦ 66◦ 42. A beam of light is emitted in a pool of water (index of refraction is n=1.33) from a depth of 62.0 cm. Where must it strike the air–water interface, relative to the spot directly above it, in order that the light does not exit the water? (See fig.) A) B) C) D) E) R>71cm R<71cm 42cm<R<50cm 35cm<R<42cm R<35cm air R H 1 1 n 43. A mirror at an amusement park shows an upright image of any person who stands 1.4 m in front of it. If the image is three times the person’s height, what is the radius of curvature? A) B) C) D) E) 1.4 m 2.4 m 3.2 m 4.2 m 5.4 m 44. Convex spherical mirrors produce images which are A) B) C) D) E) always real and smaller than the actual object always virtual and smaller than the actual object always real and larger than the actual object always virtual and larger than the actual object could be real or virtual and larger or smaller than the actual object, depending on the placement of the object Page 2 of 7 Physics 112 Exam 3 Summer 2012 45. An object is placed between a convex lens and its focal point. The image formed is A) B) C) D) E) virtual and erect virtual and inverted real and erect real and inverted could be real or virtual and erect or inverted 46. A convex lens has a focal length f. An object is placed between f and 2f on the axis. The image formed is located A) B) C) D) E) at 2f between f and 2f at f at a distance greater than 2f from the lens at a distance smaller than f 47. A 4.5-cm-tall object is placed 28 cm in front of a spherical mirror. It is desired to produce a virtual image that is upright and 3.5 cm tall. What is the focal length of the mirror? A) B) C) D) E) -38 cm -68 cm -98 cm 68 cm 98 cm 48. A parallel beam of light from a He-Ne laser, with a wavelength 656 nm, falls on two very narrow slits 0.060 mm apart. How far apart are the fringes in the center of the pattern on a screen 3.6 m away? A) B) C) D) E) 0.2 cm 0.6 cm 1.7 cm 2.8 cm 3.9 cm Page 3 of 7 Physics 112 Exam 3 Summer 2012 49. In a double-slit experiment, it is observed that the distance between adjacent maxima on a remote screen is 1.0 cm. What happens to the distance between adjacent maxima when the slit separation is cut in half? A) B) C) D) E) It increases to 2.0 cm. It increases to 4.0 cm. It increases to 8.0 cm. It decreases to 0.50 cm. It decreases to 0.25 cm. 50. When violet light of wavelength 415 nm falls on a single slit, it creates a central diffraction peak that is 9.20 cm wide on a screen that is 2.55 m away. How wide is the slit? A) B) C) D) E) 23 cm 2.3 cm 5.2 mm 5.2m 23m 51. Which color of visible light would give the best resolution in a microscope? A) B) C) D) E) Red Yellow Green Blue All colors give the same resolution 52. The first-order line of 589-nm light falling on a diffraction grating is observed at a 15.5° angle. At what angle will the third order be observed? A) B) C) D) E) 31.0° 46.5° 53.3° 62.1° 71.4° Page 4 of 7 Physics 112 Exam 3 Summer 2012 53. A lens appears greenish yellow ( 570 nm is strongest) when white light reflects from it. What minimum thickness of coating (n 1.25) do you think is used on such a glass (n 1.52) lens, and why? A) B) C) D) E) 152 nm 228 nm 320 nm 440 nm 570 nm 54. What is Brewster’s angle for an air–glass (n 1.52) surface? A) B) C) D) E) 31.2° 41.0° 45.0° 48.1° 56.7° 1 55. A light meter reports that a camera setting of 200 s at f 8 will give a correct exposure. But the photographer wishes to use f 16 to increase the depth of field. What should the shutter speed be (time shutter is open)? A) B) C) D) E) (1/50)s (1/100)s (1/200)s (1/400)s (1/800)s 56. What statement is wrong? A) B) C) D) E) Far point is farthest distance at which object can be seen clearly. Normal far point is about 25 cm. Nearsightedness means that far point is too close. Near point is closest distance at which eye can focus clearly. Farsightedness means near point is too far away. Page 5 of 7 Physics 112 Exam 3 Summer 2012 57. Reading glasses of what power are needed for a person whose near point is 115 cm, so that he can read a computer screen at 55 cm? Assume a lens–eye distance of 1.8cm. A) B) C) D) E) -1D -2D +1D +2D +3D 58. A small insect is placed 5.00 cm from a 6.00 -cm-focal-length lens. Calculate the angular magnification. A) B) C) D) E) 2 3 4 5 6 59. An astronomical telescope has an objective with focal length 85 cm and a 35-D eyepiece. What is the total magnification? A) B) C) D) E) -17 +17 -30 +30 -33 60. A microscope has a 1.8-cm-focal-length eyepiece and a 0.85-cm objective lens. The distance between the lenses is 16.0 cm. Calculate the total magnification (ignore minus sign). A) B) C) D) E) 55 83 110 150 232 Page 6 of 7 Physics 112 Exam 3 Summer 2012 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 41 51 42 52 43 53 44 54 45 55 46 56 47 57 48 58 49 59 50 60 Page 7 of 7