2.1 Waves

Question 1

Name and give an example of the 3 types of waves

Answer 1

Transverse - EM waves
Longitudinal - Sound waves
Mechanical - Seismic waves

Question 2

Give 2 similarites and differences between transverse and longitudinal waves

Answer 2

Transverse:
Oscillate perpendicular to the direction of travel
Can be polarised
Longitudinal:
Oscillate parallel to the direction of travel
Has to move through a substance
Both:
Transfer energy
Interfere with other waves

Question 3

Define polarised light

Answer 3

Light that has passed through a polarising filter which has limited the light to one plane of vibration

Question 4

Describe how the amount light passing through 2 polarising filters, initially parallel, changes as the second filter is rotated 180°

Answer 4

The amount of light will be maximun at 0°. When the filter is rotated to 90° the amount of light passing through the filters will decrease until at 90° no light will pass through. As the filter is rotated to 180° the amount of light will increase again until there is another maximun at 180°

Question 5

Define the amplitude of a wave

Answer 5

The maximum displacement a vibrating particle reaches from the position of equilibrium

Question 6

Define the wavelength of a wave

Answer 6

The distance between the same point on successive waves e.g crest to crest

Question 7

Define the period of a wave

Answer 7

The time taken for a complete wave to pass a fixed point

Question 8

Define the frequency of a wave

Answer 8

The number of complete waves that pass a stationary point in a second

Question 9

What is the phase difference of 2 particles half a wavelength apart?

Answer 9

π or 180°

Question 10

What is the phase difference of 2 particles a quarter of a wavelength apart?

Answer 10

½π or 90°

Question 11

What is the phase difference of 2 particles a full wavelength apart?

Answer 11

2π or 0/360°

Question 12

What are the 3 processes that can occur to waves?

Answer 12

They can be reflected, refracted or diffracted

Question 13

When does maximum diffraction occur?

Answer 13

When the gap is the same size as the wavelength of the wave

Question 14

What are the 2 types of interference and when do they occur?

Answer 14

Constructive interference occurs when 2 waves in phase meet and their amplitude adds to form a greater amplitude
Destructive interference occurs when 2 waves which are out of phase meet and their amplitude cancel each other out

Question 15

When is a stationary formed?

Answer 15

When a wave is reflected at its source forming 2 waves travelling in opposite directions with the same frequency

Question 16

When does the first harmonic occur?

Answer 16

When there is one antinode

Question 17

In wave equations what does L represent and what is it measured in?

Answer 17

The length of string and is measured in metres

Question 18

Define coherent souces

Answer 18

When 2 sources of waves have the same frequency and a constant phase difference

Question 19

What does T represent in wave equations and what is it measured in?

Answer 19

Tension measured in Newtons

Question 20

What does µ represent in wave equations and what is it measured in?

Answer 20

Mass per unit length measured in kg/m

Question 21

How do particles in a stationary wave vibrate?

Answer 21

They vibrate with the same frequency except those at nodes where there is no vibration

Question 22

At what amplitude to particles in a stationary wave vibrate?

Answer 22

The amplitude varies from zero at nodes to maximum on antinodes