Refraction and Diffraction

Question 1

Describe how a wave refracts

Answer 1

It changes direction upon entering a new material

Question 2

Define ‘diffraction’

Answer 2

When a waves bend around an object, causing the waves to spread out

Question 3

When does diffraction happen and what does it look like on a wave?

Answer 3

All waves spread out (diffract) at the edges when they pass through a gap or pass an obstacle

Question 4

What does the amount of diffraction depend on?

Answer 4

The size of the gap relative to the wavelength of the wave

Question 5

What causes the waves to spread out more?

(2)

Answer 5

1. A narrower gap
2. A longer wavelength

Question 6

Define a ‘narrow gap’

Answer 6

One that is the same order of magnitude as the wavelength of the wave - i.e. they’re the same size

Question 7

So what does the narrowness of a gap depend on?

Answer 7

The wavelength of the wave on question

Question 8

Can light be diffracted?

Answer 8

Yes - all EM waves can. However light has a very small wavelength, so it needs a really small gap to be diffracted

Question 9

Why does a wave refract when it meets the boundary of another material at an angle?

Answer 9

Because the speed of the wave is changed, so the side that hits the surface of the new material first moves slightly faster or slower than the side that hits it later, causing it to bend.

Question 10

Waves are only refracted if they meet a new medium ____ ____ ____

Answer 10

Waves are only refracted if they meet a new medium AT AN ANGLE

Question 11

Define ‘the normal’

Answer 11

When the angle of incidence is zero

Question 12

If a wave meets medium along the normal, what happens?

Answer 12

The wave speeds up

BUT

It does not refract