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
5.2m
23m
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
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