Module 4 - Waves (Reflection and Refraction)

Question 1

When does reflection occur (A/S/N)

Answer 1

Always

Question 2

What is a plane wave

Answer 2

A wave that propogates linearly

Question 3

What is a circular wave

Answer 3

A wave that propogates radially (Often from a point source)

Question 4

What is reflection

Answer 4

When a wave changes direction at a boundary between two media, and remains in the original media

Question 5

What is the law of reflection

Answer 5

The angle of incidence = the angle of reflection

Question 6

When you take the angle of both incidence and reflection where is it from

Answer 6

The line normal to the media boundary

Question 7

What characteristics remain unchanged during reflection

Answer 7

• The frequency of the wave
• The wavelength of the wave
• The speed of the wave

Question 8

Why doesnt the speed of the wave change during reflection

Answer 8

• The wave remains in the same medium

Question 9

Why doesnt the frequency of the wave change during reflection

Answer 9

• The frequency is determined from the source of the wave which doesnt change

Question 10

Why doesnt the wavelength of the wave change during reflection

Answer 10

• The frequency and speed are constant so because v = fλ , λ stays constant

Question 11

What is partial reflection

Answer 11

Where only part of the incident ray is reflected

Question 12

What wave property changes during partial reflection and why

Answer 12

• The amplitude. This is because some of the energy being transferred is lost during the transmission between the 2 boundaries, and so less energy is transferred to particles to oscillate

Question 13

What is a wave front

Answer 13

A line joining points on a wave that are in phase

Question 14

What does the distance between 2 adjacent wavefronts represent

Answer 14

• The wavelength

Question 15

When does refraction occur (A/S/N)

Answer 15

Sometimes

Question 16

What is refraction

Answer 16

The change in direction of a wave, due to a change in speed, as it enters a new medium at an angle, to the media boundary normal

Question 17

What is always accompanied when refraction occurs

Answer 17

• Partial reflection

Question 18

What is the rule of thumb for change in speed due to refraction

Answer 18

• If a wave slows down in the new medium it refracts towards the normal
• If a wave speeds up in the new medium it refracts away from the normal

Question 19

Why does refraction only occur at an angle

Answer 19

• At an angle part of the wave frontapproaches the new medium and changes speed whilst the other part to remain at the same speed in the original medium, this cause the change in direction, however if there was no/ an oblique angle the whole wave front would change speed at the same time

Question 20

What wave property stays constant in refraction and why

Answer 20

• The frequence –> determined at the source

Question 21

What wave property changes when refraction occurs

Answer 21

• The speed
• The wavelength as a result of the speed

Question 22

What is the relationship between the wavelength and the speed of the wave as it refracts and why

Answer 22

• v = kλ, because frequency is constant

Question 23

What medium density makes mechanical waves slow down and speed up, and what medium density makes EM waves slow down and speed up

Answer 23

Mechanical:
- Slow down –> Lower optical density
- Speed up –> Higher optical density

EM:
- Slow down –> higher optical density
- Speed up –> lower optical density