Refractive index and critical angles

Question 1

Requirements for total internal reflection

Answer 1

1) An angle above 90 degrees (critical angle).

2) The light must be travelling from a more dense medium to a less dense medium.

Question 2

What happens if the angle of incidence is less than the critical angle when shining through a semicircular block?

Answer 2

Most light passes out at a narrow angle to the flat edge but some is internally reflected.

Question 3

What happens if the angle of incidence is equal to the critical angle when shining through a semicircular block?

Answer 3

The emerging ray comes out along the flat edge and there’s a lot of internal reflection

Question 4

What happens if the angle of incidence is greater than the critical angle?

Answer 4

No light comes out . It’s all internally reflected (total internal reflection)

Question 5

How to use Snell’s law to find critical angles

Answer 5

Sin (C) = 1/n (refractive index)

Question 6

How does the critical angle change as refractive index increases?

Answer 6

It gets lower

Question 7

Uses of total internal reflection

Answer 7

1) Optical fibers

2) Prismatic periscopes