Waves 01 - 04

Question 1

What is a progressive wave?

Answer 1

It’s a periodic oscillation that transfer energy but not matter.

Question 2

What happens to the amplitude of a progressive wave as it travels?

Answer 2

It changes constantly so therefore every particle along the wave reaches the same max amplitude.

Question 3

What’s the difference between a transverse and a longitudinal wave?

Answer 3

Longitudinal waves: motion of particles is parallel to the direction of energy transfer.
Transverse waves: the plane of oscillations is perpendicular to the direction of energy transfer.

Question 4

Transverse waves examples?

Answer 4

All EM waves, water waves, waves on a string.

Question 5

Longitudinal waves examples?

Answer 5

Sound waves, P-waves (earthquakes).

Question 6

What type of wave can be polarised?

Answer 6

Light waves
Microwaves
Ultraviolet waves
Radio waves

Question 7

What does coherent mean?

Answer 7

A fixed relationship between the phase of waves in a beam of radiation of a single frequency. Two beams of light are coherent if phase difference is constant and not if they are changing or random.

Question 8

What does a graph of displacement/m against time/s of a wave show?

Answer 8

Displacement on the y axis.
Time on the x axis.
Looks like a cos graph.
A wave on the graph is the time period.

Question 9

What does a graph of displacement/m against distance/m of a wave show?

Answer 9

Displacement on the y axis.
Distance on the x axis.
Looks like a cos graph.
A wave on the graph is the wavelength.

Question 10

What will two waves with a phase difference of 30° or pi/6 or 1/12 of a circle look like on a graph?

Answer 10

Call the one that starts first A and the second that starts 30° after B. A will reach the max and min displacement quicker than B, B is almost lagging behind.

Question 11

How is a stationary wave made?

Answer 11

1. A standing wave is formed when…
2. Two waves of equal wavelength (frequency)
3. With similar amplitudes
4. Travelling in opposite directions
5. Superposition/interference occurs

Question 12

What can you say about the energy transmitted by a stationary wave?

Answer 12

They don’t, they are fixed in place, don’t travel.

Question 13

What is a node?

Answer 13

A node is where on a wave there is minimum/no displacement.

Question 14

What is an anti node?

Answer 14

An anti node is where on a wave there is the maximum displacement.

Question 15

What is the formula for the first harmonic and the pattern?

Answer 15

Fn (frequency of the nth harmonic) = F1 (frequency of 1st harmonic) x n (number of harmonic)

Question 16

What do the diagrams for the 1st harmonic look like?

Answer 16

2 nodes
1 anti node
Wavelength 2L
Frequency 50kHz

Question 17

What do the diagrams for the 2nd harmonic look like?

Answer 17

3 nodes
2 anti node
Wavelength L
Frequency 100kHz

Question 18

What do the diagrams for the 3rd harmonic look like?

Answer 18

4 nodes
3 anti node
Wavelength 2/3 x L
Frequency 150kHz

Question 19

What waves cannot be polarised?

Answer 19

Longitudinal

Question 20

Which of the following is correct for a stationary wave?

A Between two nodes the amplitude of the wave is constant.
B The two waves producing the stationary wave must always be 180° out of
phase.
C The separation of the nodes for the second harmonic is double the
separation of nodes for the first harmonic.
D Between two nodes all parts of the wave vibrate in phase.

Answer 20

D Between two nodes all parts of the wave vibrate in phase.