Deck 22: Reflection and Refraction of Light

Question 1

State the law of reflection.

Answer 1

The angle of incidence is equal to the angle of reflection.

Question 2

Describe the differences between secular and diffuse reflection.

Answer 2

Specular reflection occurs when the reflecting surface is smooth and flat. The reflected rays from parallel incident rays are also parallel. Diffuse reflection occurs when the reflecting surface is rough. The reflected rays from parallel incident rays are not parallel because of the irregular nature of the surface.

Question 3

The critical angle is given by sin_c (1/n₁) for what condition?

Answer 3

The second index n₂ =1.00

Question 4

Arrange in order of increasing wavelength: blue, green, indigo, orange, red, violet, yellow.

Question 5

The use of wave fronts and rays to describe optical phenomena is called

A) geometrical optics.
B) quantum optics.
C) dispersive optics.
D) wave optics.

Question 6

The angle of incidence can vary between zero and

A) 3 $\pi$ /2 radians.
B) $\pi$ /2 radians.
C) 2 $\pi$ radians.
D) 1 radian.
E) $\pi$ radians.

Question 7

The angle of incidence

A) is always greater than the angle of reflection.
B) must equal the angle of reflection.
C) is always less than the angle of reflection.
D) may be greater than, less than, or equal to the angle of reflection.

Question 8

When a ray of light passes obliquely from one medium to another, which of the following changes?

A) speed
B) wavelength
C) speed, direction of travel, but not wavelength
D) wavelength, speed, & direction of travel
E) direction of travel

Question 9

When a light wave enters into a medium of different optical density

A) its speed and wavelength change.
B) its frequency and wavelength change.
C) its speed and frequency change.
D) its speed, frequency, and wavelength change.

Question 10

Optical density is directly proportional to

A) light speed.
B) index of reflection.
C) index of refraction.
D) mass density.

Question 11

Which of the following materials has the slowest speed of light?

A) air
B) water
C) flint glass
D) oil
E) diamond

Question 12

An index of refraction less than one for a medium would imply that

A) the speed of light in the medium is the same as the speed of light in vacuum.
B) reflection is not possible.
C) refraction is not possible.
D) the speed of light in the medium is greater than the speed of light in vacuum.

Question 13

A ray of light, which is traveling in a vacuum, is incident on a glass plate (n = ng). For increasing angles of incidence, the angle of refraction

A) increases, approaching the limiting value of sin^-1 (1/n_g) degrees.
B) decreases, approaching the limiting value of zero degrees.
C) increases, approaching the limiting value of 90°.
D) increases, approaching the limiting value of sin^-1 (n_g) degrees.

Question 14

Shown here in Figure 22-1 are some possible paths that a light ray can follow in going either from glass to air or from air into glass.

In the drawing you are not told whether the light is going from left to right or from right to left. Which path did the light follow?

A) path C
B) path G
C) path E
D) path F
E) path D

Question 15

A light beam composed of red and blue light is incident upon a rectangular glass plate, as shown in Figure 22-2.

The light emerges into the air from point P as two separate beams

A) that are not parallel, with the blue beam displaced below the red beam.
B) that are parallel, with the blue beam displaced below the red beam.
C) that are parallel, with the red beam displaced below the blue beam.
D) that are not parallel, with the red beam displaced below the blue beam.

Question 16

Fiber optics depends upon the phenomenon of

A) dispersion.
B) polarization.
C) total internal reflection.
D) diffuse reflection.

Question 17

When TOTAL REFLECTION occurs at a surface, the incident angle must be in the substance with the higher

A) incident angle.
B) c/n.
C) index of refraction.
D) speed of light.

Question 18

For certain angles, TOTAL INTERNAL REFLECTION can occur when light tries to pass from one medium to another which has

A) a larger index of refraction.
B) an index of refraction which is sin^-1 (45°).
C) a smaller index of refraction.
D) the same index of refraction.
E) an index of refraction which is sin^-1 (n).

Question 19

Fiberscopes are based on the physical phenomena called

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

Question 20

A ray of light (inc) enters a 45° - 90° glass prism from air (bottom left), as shown in Figure 22-3.
In what direction does the light re-emerge back into the air?

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

Question 21

A light ray emerges from the bottom of a 45° glass prism into air, as shown in Figure 22-4.

From which direction was the ray incident on the prism?

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

Question 22

When the index of refraction of a transparent material varies with wavelength, the material exhibits

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

Question 23

In common transparent media, as the frequency of light increases, the index of refraction

A) varies as the sine of the incident angle.
B) increases.
C) stays constant.
D) decreases.

Question 24

Which of the following colors undergoes the greatest REFRACTION when passing from air into glass?

A) orange
B) blue
C) red
D) green
E) yellow

Question 25

You can only see a rainbow if

A) the sun is 90° to the side.
B) the sun is in front of you.
C) the sun is 180° to the side.
D) the sun is behind you.

Question 26

The color on the outer edge of the primary rainbow is

A) green
B) red
C) yellow
D) violet
E) white

Question 27

Rainbows are caused by sunlight being

A) refracted & reflected but not dispersed.
B) dispersed, refracted, & reflected.
C) reflected.
D) dispersed.
E) refracted.

Question 28

A laser beam strikes a plane reflecting surface with an angle of incidence of 37°. What is the angle between the incident ray and the reflected ray?

Question 29

If a transparent material has an index of refraction of 1.67, what is the speed of light in the material?

Question 30

Red light with a wavelength of 650. nm travels from air into a liquid with an index of 1.33. What is the frequency and wavelength in the liquid?

Question 31

A light beam enters water at an angle of incidence of 37°. Determine the angle of refraction.

Question 32

Light of wavelength 550. nm in air is found to travel at 1.96 × 10⁸ m/s in a certain liquid.
(a) Determine the index of refraction of the liquid.
(b) Determine the frequency of the light in air.

Question 33

Light of wavelength 550 nm in air is found to travel at 1.96 × 10⁸ m/s in a certain liquid. Determine
(a) the frequency of the light in the liquid.
(b) the wavelength of the light in the liquid.

Question 34

A light beam having a wavelength of 470. nm in air is directed into glycerine (n = 1.47)
(a) What is the frequency of the light in the glycerine?
(b) What is its wavelength in the glycerine?
(c) If the incident angle is 75.0°, what is the refracted angle?

Question 35

A person looks straight down into a large cube of glass. Three cm below the surface is a bubble. How far below the surface does the bubble appear to the person?

Question 36

How long does it take a light beam to cross a 6. m wide room? If the air were replaced with a transparent medium of index n, how much longer would it take?

Question 37

A point source of light is positioned 20.0 m below the surface of a lake. What is the diameter of the largest circle on the surface of the water through which light can emerge?

Question 38

A buoy, used to mark a harbor channel, consists of a weighted rod 2.00 m in length. 1.50 m of the rod is immersed in water and 0.500 m extends above the surface. If sunlight is incident on the water with an angle of incidence of 40.0°, what is the length of the shadow of the buoy on the level bottom of the harbor?

Question 39

A light ray strikes a glass plate of thickness 0.80 cm at an angle of incidence of 60°. The index of refraction of the glass is 1.55. By how much is the beam displaced from its original line of travel after it has passed through the glass?

Question 40

A light beam with wavelength 440. nm in a material then enters air and its wavelength becomes 577. nm.
(a) What is the index of refraction for the material?
(b) At what angle with the surface will the beam be totally reflected back in the material?

Question 41

Light in a transparent material (index of refraction 1.333) strikes the boundary with another transparent material (n = 1.010).
(a) What is the critical angle for total internal reflection?
(b) By what percent does the wavelength change going from the 1st to the 2nd material?

Question 42

A beam of light (f = 5 × 10¹⁴ Hz) enters a piece of glass (n = 1.5). What is the frequency of the light while it is in the glass?

A) 7.5 × 10¹⁴ Hz
B) 3.33 × 10¹⁴ Hz
C) 5 × 10¹³ Hz
D) 5 × 10¹⁴ Hz
E) 7.5 × 10¹³ Hz

Question 43

The speed of light in a certain medium is 2.2 x 10⁸ m/s. What is the index of refraction of this medium?

A) 1.0
B) 1.4
C) 1.2
D) 1.8
E) 1.6

Question 44

The index of refraction of a certain medium is 1.5. What is the speed of light in that medium?

A) 5.0 × 10⁸ m/s
B) 1.0 × 10⁸ m/s
C) 3.0 × 10⁸ m/s
D) 4.0 × 10⁸ m/s
E) 2.0 × 10⁸ m/s

Question 45

At what angle must a fish underwater look in order to see a fisherman at the shore? (Note: n for water is 1.33.)

A) 41.2°
B) 48.8°
C) 60.0°
D) 90.0°
E) 36.9°

Question 46

My flashlight beam makes an angle of 60. degrees with the surface of the water before it enters the water. In the water what angle does the beam make with the surface?

A) 30°
B) 60°
C) 22°
D) 68°
E) 0°

Question 47

An oil layer that is 5.0 cm thick is spread smoothly and evenly over the surface of water on a windless day. What is the angle of refraction in the water for a ray of light that has an angle of incidence of 45° as it enters the oil from the air above? (The index of refraction for oil is 1.15, and for water it is 1.33.)

A) 25.6°
B) 38.6°
C) 27.2°
D) 35.5°
E) 32.1°

Question 48

A beam of light, traveling in air, strikes a plate of transparent material at an angle of incidence of 56°. It is observed that the reflected and refracted beams form an angle of 90°. What is the index of refraction of this material?

A) n = 1.44
B) n = 1.53
C) n = 1.48
D) n = 1.40
E) n = 1.43

Question 49

A ray of light consisting of blue light (wavelength 480 nm) and red light (wavelength 670 nm) is incident on a thick piece of glass at 80°. What is the angular separation between the refracted red and refracted blue beams while they are in the glass? (The respective indices of refraction for the blue light and the red light are 1.4636 and 1.4561.)

A) 0.455°
B) 0.341°
C) 0.277°
D) 0.155°
E) 0.330°

Question 50

What is the critical angle for light traveling from crown glass (n = 1.52) into water (n = 1.33)?

A) 61°
B) 66°
C) 42°
D) 57°
E) 48°

Question 51

An optic fiber is made of clear plastic with index of refraction of 1.50. For what angle of incidence will light remain within the plastic "guide"?

A) >40.3°
B) >21.1°
C) >41.8°
D) >23.4°
E) >38.3°

Question 52

What is the index of refraction inside a certain transparent material if the critical angle is found to be 48.° (air is outside)?

A) 1.48
B) 1.35
C) 1.49
D) 0.743
E) 1.22

Question 53

An optical fiber is 1.00 meter long and has a diameter of 20.0 $\mu$ m. Its ends are perpendicular to its axis. Its index of refraction is 1.30. What is the minimum number of reflections a light ray entering one end will make before it emerges from the other end?

A) 2.85 × 10⁵
B) 2.56 × 10⁵
C) 2.42 × 10⁵
D) 1.85 × 10⁵
E) 2.02 × 10⁵