5 - Ray Optics

Question 1

What are the 4 principles of the ray model?

Answer 1

1) Light rays point in the direction that light is travelling.
2) Light rays travel in straight lines at the speed of light in the material.
3) Light rays continue in the same direction forever, unless they are reflected, refracted, or scattered.
4) Every point on an object is a source of light rays, whether it is reflective or self-luminous.

Question 2

What is specular reflection?

Answer 2

Specular reflection = reflection where parallel incident rays create parallel reflected rays.

Question 3

What is diffuse reflection?

Answer 3

Diffuse reflection = reflection where parallel incident rays do not create parallel reflected rays.

Question 4

What happens when light enters a second medium with a larger index of refraction
(n2 > n1)?

Answer 4

it is refracted towards the

normal (θ2 < θ1)

Question 5

What happens when light enters a second medium with a smaller index of refraction
(n2 < n1)?

Answer 5

it is refracted away from the

normal (θ2 > θ1).

Question 6

What happens if light is normally incident on a boundary.

Answer 6

does not refract and continues along its original direction of travel.

Question 7

What is a critical angle?

Answer 7

the refracted light travels parallel to the boundary between the media (θ2 = 90o).

Question 8

In only what situations can a critical angle exist?

Answer 8

A critical angle exists only for situations where n2 < n1.

Question 9

What happens when θ1= θc?

Answer 9

When θ1= θc the light travels parallel to the boundary.

Question 10

What happens when θ1> θc?

Answer 10

When θ1 > θc total internal reflection

occurs (the light does not transmit through the boundary).