Wave Boundaries, refraction and reflection

Question 1

What are the 3 things that can happen when a wave meets a boundary

Answer 1

Absorbed- the wave transfers energy to the material’s energy stores.
Transmitted- wave carries on travelling through material, often leads to refraction.
Reflected- the incoming ray is sent back away from the second material ( how echoes are created).

Question 2

What happens to a wave when it hits a boundary at an angle

Answer 2

The change of speed causes a change in direction- refraction.

Question 3

The greater the change in speed, the ______ a wave _______

Answer 3

More, bends

Question 4

The wave bends ________ the normal if it slows down and away from the normal if it _______ ___.

Answer 4

Towards, speeds up

Question 5

Electromagnetic waves like _______ usually travel more slowly in ________ materials.

Answer 5

Light, denser

Question 6

The _________ of a wave stays the same when it crosses a boundary. This means that the change in speed is caused by a change in __________. The wavelength ________ if the wave slows down and increases if it ________ ___.

Answer 6

Frequency, wavelength, decreases, speeds up.

Question 7

What’s the angle of incidence

Answer 7

The angle between the incidence ray (ray entering the medium) and the normal.

Question 8

What’s the angle of refraction

Answer 8

The angle between the refracted ray (ray leaving the medium) and the normal.

Question 9

What’s the law of reflection

Answer 9

Angle of incidence = angle of reflection

Question 10

What’s total internal reflection (TIR)

Answer 10

When a wave crossing a boundary is reflected back into the material.

Question 11

When does total internal reflection happen

Answer 11

When the wave travels through a dense material towards a less dense substance like air.

Question 12

If i is less than the critical angle

Answer 12

Most of the light is refracted into the outer layer, but some of it is internally reflected.

Question 13

If i is equal to the critical angle

Answer 13

The ray would go along the surface (with quite a bit of internal reflection)

Question 14

If i is larger than the critical angle.

Answer 14

No light comes out. It’s all internally reflected, i.e. total internal reflection.

Question 15

What’s specular reflection

Answer 15

When waves are reflected in a single direction by a smooth surface.
You get a clear reflection (mirror)

Question 16

What’s diffuse reflection and why does it happen.

Answer 16

When waves are reflected by a rough surface (paper) and the waves are reflected in all directions.
Happens because the normal is different for each incident ray, so each ray has a different angle of incidence.
The angle of incidence = angle of reflection rule still applies.
When light is reflected by something rough, the surface looks matt and you don’t get a clear reflection.