Refraction Of Waves

Question 1

How does refraction happen?

Answer 1

When a wave crosses a boundary (between two materials) at a certain angle and consequently the wave changes direction, it’s called refraction

Question 2

What does how much the wave is refracted depend on?

Answer 2

The density of the two materials that share the boundary that the wave hits

Question 3

What will happen if a wave were to go through a denser material?

Answer 3

The wave will change speed. The higher the density the slower the wave. So when a wave crosses the boundary of a dense material, the wave will usually slow down.

Question 4

“Usually the denser the material, the slower the wave will get when it crosses into the material” why is the word usually used here?

Answer 4

Because when sound waves travel across a dense material, they tend to speed up instead of slow down. And that’s because since the particles are closer together, energy can be transferred faster

Question 5

What happens when a wave meets the boundary of a material that’s not so dense?

Answer 5

The lower the density of an object, the faster the wave changes speed when it hits the boundary.

Question 6

What direction will a wave go in when it crosses a boundary of a denser material?

Answer 6

If a wave crosses into a material and slows down (high density), then the wave will bend towards the normal

Question 7

What direction will a wave go in when it crosses a boundary of a less denser material?

Answer 7

If a wave crosses into a boundary and speeds up (low density), then the wave will bend away from the normal.

Question 8

What is true about the incoming and emergent ray during refraction?

Answer 8

They are always parallel to each other

Question 9

What happens if a wave doesn’t hit a boundary at an angle, but travels along the normal before hitting the boundary?

Answer 9

Then the wave would change its speed, but it wouldn’t change direction so it’s not refracted. It would have to hit a boundary at an angle to be refracted.

Question 10

When speed changes, does the frequency and wave length of the wave also change? Why?

Answer 10

The wavelength of the wave will change with the speed, but not the frequency. Since the wavelength changed and the frequency didn’t, the speed has to change exactly how the wavelength did to make up for it. This is because wave speed = frequency times wavelength.

Question 11

Define optical density

Answer 11

Optical density: it’s a measure of how quickly light can travel through and object/material. The higher the optical density, the slower the light and vice versa.

Question 12

Explain in four steps how you’d set up a ray diagram for refraction.

Answer 12

1. Start by drawing out the boundary between the two materials that the ray is going to cross
2. Then draw a normal (dotted) line in the middle of the boundary line. The normal should be at 90 degrees to the boundary.
3. Draw an incident ray that meets the normal (at the boundary) at an angle. The angle between the ray and the normal is the angle of incidence
4. Now draw the reflected ray on the other side of the boundary line. If the second material is optically denser than the first, the wave will slow down and the wave should bend towards the normal (if this is the case, i > r). If it’s the opposite case, the wave should bend away from the normal. If this is the case then r > i.