Wave Behaviour at Boundaries

Question 1

what can happen when a wave meets a boundary between 2 materials?

Answer 1

absorbed
transmitted
reflected

Question 2

how is the wave absorbed?

Answer 2

• transfers energy to the materials energy stores
• thermal energy store, leads to heating
• used in microwaves

Question 3

how is the wave transmitted?

Answer 3

• carries on travelling through the new material
• leads to refraction
• used in communications, glasses and camera lenses

Question 4

how is the wave reflected?

Answer 4

• incoming ray is neither absorbed or transmitted
• sent back away from the second material
• how echoes are created

Question 5

what is refraction?

Answer 5

• waves changing direction at a boundary

- the greater the change in speed, the more a wave bends

Question 6

how does refraction work?

Answer 6

waves change speed in materials with different densities

Question 7

what happens if the wave hits the boundary at an angle?

Answer 7

changes speed and causes a change in direction - refraction

Question 8

what happens if the wave is travelling along the normal?

Answer 8

will change speed but it’s not refracted

Question 9

where does the wave bend?

Answer 9

• towards the normal if it slows down

- away from the normal if it speeds up

Question 10

how do electromagnetic waves travel?

Answer 10

slower in denser materials

Question 11

what does it mean if an EM wave refracts?

Answer 11

• shorter wavelengths bend more

- can lead to the wavelengths spreading more (dispersion)

Question 12

what happens to the frequency of a wave?

Answer 12

stays the same when it crosses a boundary

Question 13

what does the wave speed mean?

Answer 13

the change in speed is caused by a change in wavelength

-the wavelength decreases is the wave slows down, and increases if it speeds up