4.4 Waves

Question 1

What is amplitude

Answer 1

Maximum displacement from the equlibrium position

Question 2

What is displacement

Answer 2

Distance from the equlibrium position

Question 3

What is wavelength

Answer 3

Minimum distance between two points in phase on adjacent waves (e.g. the distance from one peak to another or trough (transverse waves) and one compression to the next (longitudinal waves) )

Question 4

What is the period of oscillation

Answer 4

The time taken for one oscillation or time taken for wave to move one whole wavelength past a given point

Question 5

What is the frequency

Answer 5

The number of wavelengths passing past one given point per unit time s-1 or Hz

Question 6

What is the wave speed

Answer 6

The distance travelled by the wave per unit time

Question 7

What is the phase of a wave

Answer 7

The phase of a wave describes how far through a cycle a wave is

Question 8

What is the phase difference

Answer 8

Is a measure of the difference in where two waves are at in their cycle. How far out of sync the oscillations at two points on a wave

Question 9

How are stationary waves formed?

Answer 9

A stationary wave is formed when two progressive waves each with the same frequency and wavelength and moving in opposite directions interfere with one another. This creates a wave which doesn’t transfer energy from one place to another.

Question 10

What are nodes

Answer 10

Nodes are points on a stationary waves that have zero amplitude

Question 11

What are anti-nodes

Answer 11

Anti-nodes are points on a stationary wave with maximum amplitude 

Question 12

What frequencies are stationary waves

Answer 12

The frequency of stationary waves can only happen at resonance frequencies.

Question 13

What are resonance frequencies

Answer 13

Resonant frequencies happen when the distance between two fix ends is an integer multiple of half wavelengths. The first resonant Frequency is called the first harmonic.

Question 14

What are the properties of the resonant frequency

Answer 14

It has two nodes and one antinode

Question 15

What is the equation for frequency (this is in the data booklet)

Answer 15

Frequency equals wave speed divided by wavelength. Therefore this relationship is proportional to wavelength for constant wave speed.

Question 16

What is the relationship between frequency and tension

Answer 16

Frequency is proportional to the square root of the tension. This relationship should be constant.

Question 17

What is path difference

Answer 17

Path difference is the difference in distance travelled by two waves to reach a point

Question 18

What is a progressive wave?

Answer 18

A progressive wave is an oscillation that travels through matter (or in some cases a vacuum), transferring energy from one place to another, but not transferring any matter. The particles in the matter vibrate as the wave passes through them, but they do not move along with the wave.

Question 19

What is a transverse wave?

Answer 19

In a transverse wave, the oscillations are
perpendicular to the direction of wave travel, such as electromagnetic waves and waves on the surface of water. The waves have peaks and troughs at the maximum and minimum points of displacement.

Question 20

What are longitudinal waves?

Answer 20

In a longitudinal wave, the oscillations are parallel to the direction of energy transfer, such as sound waves. They have areas of compression, where particles are closer together, and areas of rarefaction, where particles are more spread out.

Question 21

What is superposition?

Answer 21

When two or more progressive waves meet and overlap, they superpose, producing a single wave. The principle of superposition states when two waves meet at a point, the resultant displacement of the wave at that point is equal to the sum of the displacements of the individual waves. The resultant displacement depends on if there is constructive interference (where the individual displacements are both in the same direction, and add together) or destructive interference (where the individual displacements are in opposite directions, and counteract each other).

Question 22

How can you find out the time period of a wave using it frequency?

Answer 22

T = 1/f

Question 23

What do each of the ‘axes’ on an oscilloscope measure?

Answer 23

Vertical divisions = voltage/amplitude of the wave.

Horizontal divisions = time (can be used to find time period and frequency).

Question 24

Define refraction.

Answer 24

Refraction is when a wave bends at a boundary between two materials due to the difference in density causing it to speed up or slow down.

Question 25

What is the difference between a polarised and unpolarised wave?

Answer 25

● Polarised waves only contains waves oscillating along one axis.
● Unpolarised waves can be oscillating in any direction perpendicular to the axis of propagation.

Question 26

Describe how a ripple tank might be used to investigate diffraction

Answer 26

● Create water waves in the tank.
● Vary the size of a gap for them to pass through.
● Note how the direction of the waves passing through changes.

Question 27

Polarised light is being passed through a rotating polarisation filter. What would happen to the intensity of the light passing through?

Answer 27

It would vary from a maximum (all light passes through) when the axis of polarisation and the axis of the filter line up to a minimum (no light passes through) when the axes are perpendicular.

Question 28

How is intensity defined in terms of power?

Answer 28

Intensity is power / area.

Question 29

How are intensity and amplitude related?

Answer 29

Intensity is proportional to amplitude2

Question 30

Are the magnetic field and electric field in a electromagnetic wave are parallel to each other.

Answer 30

No, The electric and magnetic field are at right angles to each other. Having no effect on each other

Question 31

Define coherence.

Answer 31

Coherent waves have the same frequency and wavelength and a fixed phase difference (often zero in exam questions).