3: Waves

Question 1

What is the frequency of a wave?

Answer 1

How many waves there are per second.

Question 2

Where can you find the amplitude on a wave?

Answer 2

From the equilibrium position to the crest of a wave.

Question 3

What is wavelength?

Answer 3

It describes the same point in a cycle.

Question 4

What are progressive waves?

Answer 4

Waves which transfer energy from one place to another. However, the particles within the wave do NOT move.

Question 5

What is the time period of a wave?

Answer 5

The time taken for 1 complete oscillation.

Question 6

What are circular wave fronts?

Answer 6

Waves which come from a point source, they propagate radially and in 3D they would form spheres.

Question 7

What is the wave speed equation?

Answer 7

wave speed = wavelength / time period

Question 8

What is the frequency equation?

Answer 8

Frequency = 1 / time period

Question 9

What is the speed of light?

Answer 9

3 x 10^8 m/s OR ms^-1

Question 10

What is phase difference?

Answer 10

It can be described using wavelength. We measure what phase a point is on in degrees.

Question 11

What is the equation for phase difference?

Answer 11

phase difference = phase a - phase b

Question 12

What is the idea of radians?

Answer 12

A full circle can be split into radians.
90 degrees - Pi/ 2 rad
180 degrees - Pi rad
270 degrees - 3 x Pi / 2 rad
360 degrees - 2 Pi rad

Question 13

What are the equations for arc length?

Answer 13

(Pi x diameter) x angle given / 360
radius x angle given

Question 14

What is it called when particles are half a wavelength out of phase?

Answer 14

Antiphase.

Question 15

What is it called when particles are a whole wavelength out of phase?

Answer 15

in phase.

Question 16

What are transverse waves?

Answer 16

When particles oscillate perpendicular to the direction of energy transfer. E.g. water waves.

Question 17

What are longitudinal waves?

Answer 17

When particles oscillate parallel to the direction of energy transfer. They contain compressions and rarefactions. E.g. sound waves.

Question 18

What is polarisation?

Answer 18

A feature of transverse waves only. A wave is plane polarised if all vibrations in the wave are in a single plane, which is perpendicular to the direction of propagation of the wave.

Question 19

What are standing waves?

Answer 19

Where waves appear to be still.

Question 20

How are standing waves formed?

Answer 20

When two coherent progressive waves are superposed. They must be:
- equal frequency
- nearly or the same amplitude
- same speed
- travelling in opposite directions

Question 21

What are nodes?

Answer 21

Points at which no displacement occurs.

Question 22

What are antinodes?

Answer 22

Points at which maximum displacement occurs.

Question 23

What is interference?

Answer 23

When two waves interact with each other.

Question 24

What is superposition?

Answer 24

The resultant wave due to the interference.

Question 25

When do waves interfere?

Answer 25

When they are in the same medium.

Question 26

What is constructive interference?

Answer 26

When waves in phase interfere with each other.

Question 27

What is destructive interference?

Answer 27

When waves are in antiphase and interfere with one another.

Question 28

When can standing waves exist?

Answer 28

If the wavelength always is a multiple of the distance between the fixed points.

Question 29

What is the equation for the first harmonic?

Answer 29

1/ 2 x length x square root of tension / mass per unit length

Question 30

What is the equation for mass per unit length?

Answer 30

mass / length

Question 31

What affects the first harmonic?

Answer 31

• length
• tension
• mass per unit length