Physics 112
Exam 3
Summer 2015
Name_________________
Physics 112
Summer 2015
Exam 3
Monday, July 27
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, the exam itself, and scratch paper
that you used for the exam.
Good luck!
Page 1 of 7
Physics 112
Exam 3
Summer 2015
41. A beam of light in air strikes a slab of glass (n  1.50) at a 30.0° angle to the vertical. What is
the angle of refraction?
A.
B.
C.
D.
E.
30.0°
25.7°
19.5°
15.0°
10.3°
42. A diver shines a flashlight upward from beneath the water at a 60.0° angle to the vertical.
Index of refraction water is 1.33. At what angle does the light leave the water?
A.
B.
C.
D.
E.
60°
50°
40°
30°
It does not leave the water
43. The speed of light in a certain substance is 89% of its value in water. What is the index of
refraction of this substance?
A.
B.
C.
D.
E.
1.00
1.21
1.49
1.60
3.00
44. Which statement concerning mirrors is wrong?
A.
B.
C.
D.
E.
Real image is always inverted
Inverted image is always real
Virtual image is always erect
Erected image is always virtual
Real and virtual images could be erect or inverted
Page 2 of 7
Physics 112
Exam 3
Summer 2015
45. Which statement concerning lenses is wrong?
A.
B.
C.
D.
E.
Real image is always inverted
Inverted image is always real
Virtual image is always erect
Erected image is always virtual
Real and virtual images could be erect or inverted
46. A 4.0-cm-tall object is placed 10 cm in front of a spherical mirror. It is desired to produce a
virtual image 6.0 cm tall. What is the focal length of the mirror?
A.
B.
C.
D.
E.
30 cm
25 cm
20 cm
15 cm
10 cm
47. Find magnification, if a real image is located at the same distance from a mirror as the
object?
A.
B.
C.
D.
E.
1
-1
2
-2
It is impossible to have this kind of image
48. Parallel light rays are directed from air into a double convex glass lens. These rays will
converge at:
A.
B.
C.
D.
E.
Focal point
Two focal distances from the lens
One half of the focal from the lens
At the center of the lens
On the surface of the lens
Page 3 of 7
Physics 112
Exam 3
Summer 2015
49. Monochromatic light falls on two very narrow slits. Successive fringes on a screen 5.00 m
away are 6.5 cm apart near the center of the pattern. What is the distance between the slits if
the wavelength of the light is 650 nm?
A.
B.
C.
D.
E.
500 µm
100 µm
50 µm
25 µm
5.0 µm
50. Monochromatic light falls on a slit that is 2.60  10 3 mm wide. If the angle between the first
dark fringes on either side of the central maximum is 30.0° (dark fringe on one side to dark
fringe on another side), what is the wavelength of the light used?
A)
B)
C)
D)
E)
450 nm
511 nm
585 nm
627 nm
673 nm
51. The separation between adjacent maxima in a double-slit interference pattern using
monochromatic light is
A)
B)
C)
D)
E)
Greatest for red light
Greatest for green light
Greatest for blue light
The same for all colors of light
It is smallest for green light
.
52. A 3500 lines/cm grating produces a third-order fringe at a 28.0° angle. What wavelength of
light is being used?
A)
B)
C)
D)
E)
421 nm
447 nm
502 nm
631 nm
680 nm
Page 4 of 7
Physics 112
Exam 3
Summer 2015
53. An important reason for using a very large diameter objective in an astronomical telescope is
A)
B)
C)
D)
E)
To increase the magnification
To increase the resolution
To form a virtual image
To form a real image
To increase the width of the field of view
54. A lens appears greenish yellow (   570 nm is strongest) when white light reflects from it.
What minimum thickness of coating n=1.25 is used on such a glass (n  1.52) lens?
A)
B)
C)
D)
E)
570 nm
512 nm
450 nm
321 nm
228 nm
55. What is Brewster’s angle for a diamond submerged in water if the light is hitting the diamond
(n  2.42 ) while traveling in the water (n =1.33)?
A)
B)
C)
D)
E)
33°
41°
52°
61°
72°
56. What kinds of image observe people wearing glasses?
A)
B)
C)
D)
E)
Always real
Always virtual
Real if glasses’ power is positive, and virtual if glasses’ power is negative
Real if glasses’ power is negative, and virtual if glasses’ power is positive
It could be real and virtual for any power of glasses
Page 5 of 7
Physics 112
Exam 3
Summer 2015
57. A person has a far point of 14 cm. What power glasses would correct this vision if the glasses
were placed 2.0 cm from the eye?
A)
B)
C)
D)
E)
+2.0
-2.0
-4.6
-6.5
-8.3
58. A nearsighted person wears contact lenses whose power is -5.0D. What is the person's far
point?
A)
B)
C)
D)
E)
5 cm
10 cm
20 cm
50 cm
1.0 m
59. A small insect is placed 5.0 cm from a  6.00-cm-focal -length lens. Calculate the angular
magnification.
A)
B)
C)
D)
E)
1.2
2.4
4.1
5.0
6.0
60. 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)
-15
-20
-30
-35
-41
Page 6 of 7
Physics 112
Exam 3
Summer 2015
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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