Chapter 8 - Refraction

Question 1

Define “refraction”

Answer 1

The bending of light when it passes from one medium to another

Question 2

Why does light bend?

Answer 2

Light bends when it enters another medium because the speed of light changes when it enters the other medium

Question 3

Define “refractive index” of a medium

Answer 3

The ratio of the speed of light in vacuum (c) to the speed of light in that medium (v)
n = c/v

Question 4

When a ray of light travels from a medium of lower refractive index to a medium of higher refractive index, it ________ the normal

Answer 4

bends towards

Question 5

When a ray of light travels from a medium of higher refractive index to a medium of lower refractive index, it ________ the normal

Answer 5

bends away from

Question 6

Refractive index of vacuum (or air)

Answer 6

1.00

Question 7

As light travels from vacuum (or air) into other media, it ________ the normal

Answer 7

bends towards

Question 8

As light travels from other media into vacuum (or air), it ________ the normal

Answer 8

bends away from

Question 9

The larger the angle of deviation, the ________ the ray is refracted from its original direction

Answer 9

greater

Question 10

Materials with higher refractive index are described as optically ________

Answer 10

denser

Question 11

Materials with lower refractive index are described as optically ________

Answer 11

less dense

Question 12

State the laws of refraction

Answer 12

• The incident ray, refracted ray, and the normal at the point of incidence all lie on the same plane
• The ratio of the sine of the incident angle to the sine of the angle of refraction (sin i / sin r) is a constant

Question 13

State Snell’s law

Answer 13

n1sinθ1 = n2sinθ2

Question 14

State the principle of reversibility

Answer 14

The light ray will travel along the same path regardless of which direction it started from

Question 15

Whenever a light ray reaches a surface and refracts, part of the light will be ________

Answer 15

partially reflected

Question 16

Define “critical angle”

Answer 16

The angle of incidence in the medium with higher refractive index for which the angle of refraction in the medium with lower refractive index is 90°

Question 17

Formula relating n and c

Answer 17

n = 1 / sin c

Question 18

When the angle incidence is increased beyond the critical angle, refraction ________, because r cannot increase to _______.
Instead, ________ occurs.

Answer 18

can no longer occur
more than 90°
total internal reflection

Question 19

What are the conditions required for total internal reflection to occur?

Answer 19

1. The light ray must travel from a material with higher refractive index towards a material with lower refractive index
2. The angle of incidence of the light ray must be greater than the critical angle of the medium