Deck 34: Reflection, Refraction, and Optics

Question 1

If the angle of incidence were not equal to the angle of reflection, the distance traveled by a light ray going on a path composed of two straight-line segments intersecting at the reflecting surface would be

A) greater than it is for the actual path.
B) the same as the actual path.
C) less than it is for the actual path.
D) Any on the above answers may be valid, depending on further geometric details.

Answer 1

greater than it is for the actual path.

Question 2

If a material has an index of refraction of 1.33, the speed of light through it is

A) 1.70 * 10⁸ m/s.
B) 2.26* 10⁸ m/s.
C) 3.00 * 10⁸ m/s.
D) 3.99* 10⁸ m/s.
E) 5.30* 10⁸ m/s.

Answer 2

2.26* 10⁸ m/s.

Question 3

Light travels fastest

A) in a vacuum.
B) through water.
C) through oil.
D) through diamond.
E) through glass.

Answer 3

in a vacuum.

Question 4

An oil layer that is 4.0 cm thick is spread smoothly and evenly over the surface of water on a windless day. The angle of refraction in the water for a ray of light that has an angle of incidence of 45^o as it enters the oil from the air above is 32^o. (The index of refraction for oil is 1.15, and for water it is 1.33.) If the layer of oil becomes thicker, the angle of refraction in the water

A) increases.
B) stays the same.
C) decreases.
D) More information is needed to work out the answer.

Question 5

A spherical air bubble is embedded in a glass slab. An incident ray of light approaches the bubble as shown in the figure. After passing through the air bubble, the ray of light follows the path labeled.

A) A
B) B
C) C
D) D
E) E

Question 6

Total internal reflection occurs from an interface when the ray is incident

A) from a less dense medium.
B) from a denser medium.
C) Either of the first two responses can be valid.
D) Total internal reflection does not depend on the density of the medium.

Question 7

The principle on which fiber optics is based is

A) reflection.
B) refraction.
C) dispersion.
D) total internal reflection.
E) polarization.

Question 8

When light crosses the boundary between media, the characteristic of the light that remains unchanged is

A) frequency.
B) speed.
C) wavelength.
D) None of the above.

Question 9

A diver shines an underwater searchlight at the surface of the water (index of refraction 1.33) from below. The incident angle (relative to the surface of the water) for which the light will be totally reflected is

A) 41^o.
B) 21^o.
C) 11^o.
D) All of the above are correct.
E) None of the above is correct.

Question 10

A diver swimming below the surface of a pond (index of refraction for water is 1.33) watches a light placed directly above his head, 50 cm above the water surface. The light appears to be placed

A) 37.6 cm above the surface of the pond.
B) 50.0 cm above the surface of the pond.
C) 66.5 cm above the surface of the pond.
D) None of the above is correct.

Question 11

A fish is 50.0 cm below the surface of a pond (index of refraction for water is 1.33). For a viewer directly above the fish, the fish appears to be placed

A) 37.6 cm below the surface of the pond.
B) 50.0 cm below the surface of the pond.
C) 66.5 cm below the surface of the pond.
D) None of the above is correct.

Question 12

The color humans perceive depends primarily on the property of light we call

A) frequency.
B) speed.
C) wavelength.
D) All of the previous responses are correct.
E) None of the previous responses is correct.

Question 13

When light is dispersed by an ordinary glass prism, the color with its path deviated least from its original direction is

A) blue.
B) green.
C) red.
D) All colors undergo the same deviation.
E) None of the colors undergo any deviation.

Question 14

Suppose the Earth's atmosphere can be modeled by a series of cells of air with flat interfaces and indexes of refraction increasing with depth below the "top" (upper) surface. A ray strikes the upper surface at some nonzero angle with respect to the surface normal. As it comes toward the Earth, the ray direction will

A) continue to change such that its direction will deviate more and more (from its original direction) as it travels deeper into the atmosphere, but will never curve across the normal at the local surface.
B) continue to change such that its direction will deviate more and more (from its original direction) as it travels deeper into the atmosphere, even curving across the normal at the local surface if the initial conditions are right.
C) reverse its change compared to the original refraction it experiences on its initial encounter with the atmosphere, but will never curve back to cross a line parallel to the original direction at the top surface.
D) reverse its change compared to the original refraction it experiences on its initial encounter with the atmosphere, even curving back to cross a line parallel to the original direction at the top surface if the initial conditions are right.
E) More information is needed to work out the answer.

Question 15

Suppose the Earth's atmosphere can be modeled by a series of cells of air with spherically shaped interfaces and indexes of refraction increasing with depth below the "top" (upper) surface. A ray strikes the upper surface at some nonzero angle with respect to the surface normal. As it comes toward the Earth, the ray direction will cause

A) a more drastic curvature than a flat interface.
B) a less drastic curvature than a flat interface.
C) no change from the curvature produced by a flat interface.
D) None of the previous responses is correct.
E) More information is needed to work out the answer.

Question 16

The apparent shape of the Sun near the horizon is

A) perfectly circular.
B) squashed at the edges closest and farthest from the horizon.
C) elongated at the edges closest and farthest from the horizon.
D) perfectly rectangular.

Question 17

The image seen in a plane mirror is

A) real and upright, and left and right are interchanged.
B) real and inverted, and left and right are not interchanged.
C) virtual and upright, and left and right are interchanged.
D) virtual and inverted, and left and right are not interchanged.
E) virtual and inverted, and left and right are interchanged.

Question 18

A 2.00-m-tall clown looks at himself in a full-length (floor-to-ceiling) mirror. The image of his feet is placed

A) at the bottom of the mirror.
B) 0.250 m above the floor.
C) 0.500 m above the floor.
D) 1.00 m above the floor.
E) 1.50 m above the floor.

Question 19

When you approach a vertical plane mirror at a speed of 1.0 m/s, you approach your image at a speed of

A) 2.0 m/s.
B) 1.0 m/s.
C) 0.50 m/s.
D) 0.25 m/s.
E) More information is needed to work out the answer.

Question 20

Two plane mirrors make an angle of 58^o. A light ray enters the system and is reflected once off each mirror. The ray is turned to

A) 60^o.
B) 120^o.
C) 150^o.
D) 180^o.
E) 210^o.

Question 21

A concave mirror with a radius of 20 cm creates a real image 30 cm from the mirror. The object is placed

A) 7.5 cm in front of the mirror.
B) 15 cm in front of the mirror.
C) 30 cm in front of the mirror.
D) 15 cm behind the mirror.
E) 7.5 cm behind the mirror.

Question 22

A concave mirror with a radius of 20 cm creates an image at infinity. The object was placed

A) 40 cm in front of the mirror.
B) 20 cm in front of the mirror.
C) 10 cm in front of the mirror.
D) at infinity in front of the mirror.
E) at infinity behind the mirror.

Question 23

When an object is placed 10 cm in front of a convex mirror, its virtual image is placed 5.0 cm away from the mirror. When the same object is placed 5.0 cm in front of the same convex mirror, the image is placed

A) 2.5 cm in front of the mirror.
B) 5.0 cm in front of the mirror.
C) 10 cm in front of the mirror.
D) 5.0 cm behind the mirror.
E) 2.5 cm behind the mirror.

Question 24

An object is placed 20 cm in front of a convex mirror of radius 20 cm. The image is

A) real, upright, and as large as the object.
B) virtual, upright, and as large as the object.
C) real, inverted, and as large as the object.
D) virtual, inverted, and as large as the object.
E) virtual, inverted, and larger than the object.

Question 25

A convex lens made of air (enclosed by a very thin rigid material) and used below the surface of the water will result in a

A) converging lens.
B) diverging lens.
C) lens of infinite focal distance.

Question 26

Spherical aberration is a description of the fact that a spherical mirror has a focal length (call it f_f) for light striking it far from the central axis that differs from the focal length (call it f_c) for light striking it close to the central axis. By taking the "limiting" case of a hemisphere it becomes clear that

A) f_f < f_c for the outer rays not "far" from as well as for outer rays farther from the central axis.
B) f_f < f_c for the outer rays not "far" from the central axis, and f_f > f_c for outer rays farther from the central axis.
C) f_f > f_c for the outer rays not "far" from the central axis, and f_f < f_c for outer rays farther from the central axis.
D) f_f > f_c for the outer rays not "far" from as well as for outer rays farther from the central axis.

Question 27

For a simple converging lens of ordinary glass, the focal length for red light is related to the focal length (call it f_b) for blue light by the relation

A) larger than the focal length for blue light.
B) equal to the focal length for blue light.
C) less than the focal length for blue light.
D) None of the previous answers is correct.

Question 28

A small object is placed 12 cm in front of a converging lens with a focal length of 3.0 cm. The image will be

A) real and inverted.
B) real and upright.
C) virtual and inverted.
D) virtual and upright.

Question 29

A small object is placed 12 cm in front of a diverging lens with a focal length of 3.0 cm. The image will be

A) real and inverted.
B) real and upright.
C) virtual and inverted.
D) virtual and upright.

Question 30

A thin converging lens is used to form a real image of an object placed between the focal point and the lens. The object is moved closer to the lens. The new image

A) is closer to the lens and larger.
B) is closer to the lens and smaller.
C) is farther away from the lens and smaller.
D) is farther away from the lens and larger.

Question 31

A lens is used to image an object onto a screen. When the upper half of the lens is covered,

A) the upper half of the image disappears.
B) the lower half of the image disappears.
C) the image becomes blurred.
D) the image becomes fainter.
E) the entire image disappears.

Question 32

A double concave lens has radii of curvature of 15.0 cm and 10.0 cm. An object placed 14.0 cm from the lens forms a virtual image, twice as large as the object. The index of refraction of the material the lens is made of is

A) 2.80.
B) 1.50.
C) 1.21.
D) 1.07.
E) 1.33.

Question 33

The image of a flower on a 35-mm color slide is 2.0 mm high. It is to be projected onto a screen 5.0 m from the slide, and it is to appear 50.0 cm high. The distance between the lens and the slide is

A) 2.0 mm.
B) 2.0 cm.
C) 2.0 m.
D) 1.3 cm.
E) 1.3 m.

Question 34

The image of a flower on a 35-mm color slide is 2.00 mm high. It is to be projected onto a screen 5.00 m from the slide, and it is to appear 50.0 cm high. The focal length of the lens used is

A) 1.99 m.
B) 2.00 m.
C) 2.01 m.
D) 502 m.
E) 498 m.

Question 35

The radius of curvature of a plano-convex lens made of glass (index of refraction 1.65) is 25 cm. The lens is

A) diverging, and its focal length is 38 cm.
B) diverging, and its focal length is 25 cm.
C) diverging, and its focal length is 15 cm.
D) converging, and its focal length is 25 cm.
E) converging, and its focal length is 38 cm.

Question 36

When a plano-concave lens made of glass (index of refraction 1.65) is placed in water (index of refraction 1.33), its focal length

A) increases.
B) decreases.
C) stays the same.
D) becomes zero.

Question 37

A certain converging lens has a focal length of 25 cm. To obtain a combination of power of 3.0 diopters, the lens should be combined with a second

A) diverging lens of focal length 5.0 cm.
B) diverging lens of focal length 8.0 cm.
C) diverging lens of focal length 100 cm.
D) converging lens of focal length 100 cm.
E) converging lens of focal length 8.0 cm.

Question 38

Two converging lenses of focal lengths 100 cm and 10 cm are combined to form an astronomical telescope. Its magnification is

A) 8.0.
B) 9.0.
C) 10.
D) 11.
E) 12.

Question 39

A farsighted eye requires a 2.0-diopter lens to read comfortably from a book (held 25 cm in front of the eyes). The near point of the eye without the lens is

A) +0.400 diopters.
B) +2.50 diopters.
C) -2.50 diopters.
D) -0.400 diopters.

Question 40

In nearsightedness, the rays passing through the eye converge before they reach the retina. To correct this, all of the following are valid (although not necessarily practical) means except for

A) inserting a negative lens in front of the eye.
B) relaxing the muscles that control the shape of the crystalline lens of the eye so that the lens flattens somewhat.
C) decreasing the index of refraction of the cornea and aqueous humor that covers the crystalline lens of the eye.
D) All of the above are true.

Question 41

A hypermetropic eye cannot focus on objects that are more than 2.50 m away from it. The power of the lens used to correct this vision defect is

A) +0.400 diopters.
B) +2.50 diopters.
C) -2.50 diopters.
D) -0.400 diopters.

Question 42

By changing the separation distance between lens and film, a camera can focus on subjects at a variety of distances. Assume that the lens-film separation for taking an in-focus picture of a distant object is d₀. To take an in-focus picture of a nearby object, the lens-film separation is

A) less than d₀.
B) equal to d₀.
C) greater than d₀.

Question 43

Ordinarily, light microscopes using magnifications greater than about 2000 are not built because the light received would be too

A) dim.
B) bright.
C) much refracted.
D) strongly diffracted.

Question 44

A person uses two microscopes to view the same object. Microscope A is twice as long as microscope B, and its lenses have focal lengths half as large as those in microscope B. The magnification provided by microscope B is

A) eight times as large as the magnification of microscope A.
B) two times as large as the magnification of microscope A.
C) the same as the magnification of microscope A.
D) one-half as large as the magnification of microscope A.
E) one-eighth as large as the magnification of microscope A.

Question 45

To construct an astronomical telescope, the separation between the two converging lenses of focal lengths 100 cm and 10 cm should be

A) 10 cm.
B) 90 cm.
C) 100 cm.
D) 110 cm.