Chapter 18.3- Refraction

Question 1

What two things happen when a light ray crosses the boundary between the air and the glass?

Answer 1

1. Part of the light reflects from the boundary (it obeys the law of reflection; this is how you’re able to see reflections from pools of water or storefront windows, even though water and glass are transparent)
2. Part of the light continues into the second medium and is transmitted.

Question 2

What is refraction?

Answer 2

The transmission of light from one medium to another, but with a change in direction

Question 3

Where does reflection occur?

Answer 3

At the boundary. But Reflection from the boundary between transparent media is usually very weak and is ignored here, because the goal of this section is to understand refraction.

Question 4

What is the angle of refraction?

Answer 4

The angle on the transmitted side, that is measured from the normal

Question 5

What law do we use for refraction between two media?

Answer 5

Snell’s law

Question 6

What does the index of refraction, n, for different mediums indicate?

Answer 6

It determines how much a light ray is bent when crossing the boundary between two different media. This is a consequence of the change in the speed of light as it crosses a boundary.

Question 7

Snell’s law shows:

When a ray is transmitted into a material with a higher index of refraction,….?

Answer 7

it bends to make a smaller angle with the normal

Question 8

Snell’s law shows:

When a ray is transmitted into a material with a lower index of refraction,….?

Answer 8

It bends to make a larger angle with the normal

Question 9

When does Total internal reflection (TIR) occur?

Answer 9

TIR occurs when a light ray is unstable to refract through a boundary.
Instead, 100% of the light reflects from the boundary.

Question 10

Crossing the boundary into a material with a lower index of refraction causes the ray to…??

Answer 10

It causes the ray to bend away from the normal

Question 11

The fraction of light energy that is transmitted decreases while….?

Answer 11

The fraction reflected increases.

Question 12

As angle theta(1) increases, the refraction angle theta(2)…?

Answer 12

Approaches 90 degrees

Question 13

What occurs if n2 > n1?

Answer 13

There is no critical angle and no total internal reflection

Question 14

When is a critical angle reached?

Answer 14

Theta(C) is reached when theta(2) equals 90 degrees

Question 15

What light is there at the critical angle?

Answer 15

Only reflected light. The refracted light vanishes at the critical angle.