Waves

Question 1

What is the period of a wave?

Answer 1

The time it takes for a source to produce one wave.

Question 2

What is the wave equation?

Answer 2

Speed (V m/s) = frequency (f hertz) x wavelength (l metres)

Question 3

How do you work out the period of a wave?

Answer 3

f = 1 / t

Question 4

What is an example of a longitudinal wave?

Answer 4

1. Sound waves
2. Shock waves e.g. some seismic waves
3. A slinky spring when you push one end

Question 5

What is an example of a transverse wave?

Answer 5

1. Light waves and all other EM waves
2. Waves travelling on the surface of water (ripples on water)
3. Waves on strings
4. A slinky spring wriggled up and down

Question 6

What is a transverse wave?

Answer 6

Is when the direction of energy transferred is perpendicular to the direction of vibrations.

Question 7

What is a longitudinal wave?

Answer 7

Is when the direction of energy transferred is parallel to the direction of vibrations.

Question 8

What is the amplitude of a wave?

Answer 8

The maximum height of disturbance from the undisturbed position.
louder=higher amplitude

Question 9

What is the wavelength of a wave?

Answer 9

Is the distance from one maximum disturbance to the next (peak to peak or trough to trough).
Higher pitch=shorter wavelength

Question 10

What is the frequency of a wave?

Answer 10

The number of vibrations of the source in one second.

Or the number of waves passing a particular point each second.

Question 11

Describe reflection

Answer 11

When a wave strikes a straight or flat barrier, the angle of incidence is equal to the angle of reflection.

Question 12

What do all waves do?

Answer 12

Waves transfer energy and information without transferring matter

Question 13

What happens as a wave strikes a concave barrier?

Answer 13

The waves become more curved, and are made to converge and there is no change in wavelength.
Example: Radio telescopes are concave so signals received are made to converge onto a detector.

Question 14

What happens as a wave strikes a convex barrier?

Answer 14

The waves are made to diverge (spread out) and there is no change in wavelength.

Question 15

Describe refraction

Answer 15

Refraction is when the speed that the waves are moving changes (and so does their direction), because the waves have travelled into a different medium (e.g. water and air or into denser water)

Question 16

Describe diffraction

Answer 16

1. Diffraction is when waves spread out after moving through a barrie/pass an edge
2. For example sound waves diffract when they pass through a barrier / doorways
3. Diffraction also happens when waves pass a single edge (think as just one very large gap)
4. An example of diffraction around an edge includes radio waves that are diffracted as they pass over hills.

Question 17

What affects diffraction?

Answer 17

• The amount of diffraction depends on the size of the gap relative to the wavelength of the wave
• The narrower the gap, or the longer the wavelength the more the waves spread out
• Waves can be diffracted through gaps and that the extent of diffraction depends on the wavelength and the physical dimension of the gap
• The effect is most noticeable when the wavelength of the waves is approximately equal to the size of the aperture (hole) through which they are moving

Question 18

What size gaps do harbours want?

Answer 18

Harbours want a larger gap because then the waves will cause less disturbance (not so curved waves)

Question 19

What happens when waves encounter obstacles?

Answer 19

• When waves encounter obstacles (e.g. radio waves passing hills and tall buildings), diffraction is what causes them to bend around the obstacle.
• The longer the wavelength, the more they diffract and bend around.