4. Waves

Question 1

What do waves transfer?

Answer 1

Waves transfer energy and information.

Question 2

What do waves not transfer?

Answer 2

Waves do not transfer matter.

Question 3

What are the two types of wave?

Answer 3

• Transverse
• Longitudinal

Question 4

What is a transverse wave?

Answer 4

A wave for which the oscillations are perpendicular to the direction of energy transfer.

Question 5

What is a longitudinal wave?

Answer 5

A wave for which the oscillations are parallel to the direction of energy transfer.

Question 6

Give three examples of transverse waves.

Answer 6

• Electromagnetic waves
• Seismic S-waves
• Ripples in water

Question 7

Give two examples of longitudinal waves.

Answer 7

• Sound waves
• Seismic P-waves

Question 8

What are the two parts of a longitudinal wave called?

Answer 8

Compressions and rarefactions.

Question 9

What are the two parts of a transverse wave called?

Answer 9

Peaks and troughs.

Question 10

What is a wave’s amplitude?

Answer 10

The maximum displacement of a point on a wave from its undisturbed position.

Question 11

What is wavelength?

Answer 11

• The distance from a point on a wave to the same position on the adjacent wave.
• Most commonly peak to peak or trough to trough.

Question 12

What is the frequency of a wave?

Answer 12

The number of waves that pass a given point each second.

Question 13

What is the unit used for frequency?

Answer 13

Hertz, Hz

Question 14

What is meant by a frequency of 200Hz?

Answer 14

200 waves pass a given point each second.

Question 15

What is wave speed?

Answer 15

The speed at which energy is transferred through a medium.

Question 16

What is wave velocity?

Answer 16

Wave velocity (measured in metres per second) is equal to the product of the wavelength and frequency of the wave.

Question 17

What is meant by the period of the wave?

Answer 17

The length of time it takes for one full wave to pass through a point.

period = 1 / frequency

Question 18

What word is used to describe when a wave bounces off a surface?

Answer 18

Reflection

Question 19

What is the normal (in terms of reflection and refraction)?

Answer 19

A vertical imaginary line which is perpendicular to the boundary.

Question 20

What occurs when light is reflected off a boundary?

Answer 20

It bounces off a smooth flat surface so that the angle of incidence (the angle it comes in at) is the same as the angle of reflection (the angle it leaves at).

Question 21

What is refraction?

Answer 21

Refraction is the change in speed of a wave as it reaches a boundary between two materials at an angle to the normal, usually resulting in a change in direction.

Question 22

What occurs when light is refracted at a boundary?

Answer 22

• The light changes speed and direction in the new medium.
• If the new medium is more dense, the light will travel slower and bend towards the normal.
• If the new medium is less dense, the light will travel faster and bend away from the normal.

Question 23

When entering a denser material, light waves …

Answer 23

… slow down and bend towards the normal.

Question 24

When entering a less dense material, light waves …

Answer 24

… speed up and bend away from the normal.

Question 25

How can refraction be measured?

Answer 25

The angle of incidence, i, and angle of refraction, r, can be measured and compared. All angles are measured relative to the normal.

Question 26

What are the effects of absorption of different wavelengths of waves in different mediums?

Answer 26

• Some materials behave differently depending on the wavelength.
• An example is glass which will transmit visible light, but reflect UV light.

Question 27

How do sound waves travel through a solid?

Answer 27

The particles in the solid vibrate and transfer kinetic energy through the material.

Question 28

Does frequency change during refraction?

Answer 28

Frequency never changes during refraction.