Waves

Question 1

What does the term wavelength mean?

Answer 1

The distance between the same points on two consecutive waves. (metre-m).

Question 2

What does the term amplitude mean?

Answer 2

The distance from equilibrium line to the crest or trough.

Question 3

What does the term frequency mean?

Answer 3

The number of waves that pass a single point per second. (Hertz-Hz).

Question 4

What does the term period mean?

Answer 4

The time taken for a whole wave to completely pass a single point.

Question 5

What does the term wave front mean?

Answer 5

The plane in which the wave travels (ie direction of the wave).

Question 6

What is the relationships within waves? (4)

Answer 6

1. Increase frequency, velocity increases
2. Wavelength increases, velocity increases
3. Period is inversely proportional to frequency
4. Smaller period, higher frequency, greater velocity

Question 7

What are transverse waves? (3)

Answer 7

1. Light, or any EM waves, seismic S waves, water waves
2. Has peaks and troughs
3. Vibrations/oscillations that travel perpendicular to the direction of the wave.

Question 8

What are longitudinal waves?

Answer 8

1. Sound waves, seismic P waves
2. Has compressions and rarefactions
3. Vibrations/oscillations that are parallel to the direction of travel

Question 9

What are some examples of how to measure sound in air? (2)

Answer 9

1. Make a noise at ~50m from a solid wall and record time for the echo to be heard, then use speed=distance/time.
2. Have two microphones connected to a datalogger at a large distance apart and record time difference between a sound passing from one to the other – then use speed=distance/time.

Question 10

What is refraction?

Answer 10

When waves pass into a more optically dense medium (air to glass), the wave will be refracted at the boundary and will change direction to bend towards the normal.
The speed and wavelength decreases. Energy of a wave is constant.

Question 11

What is transmission of waves?

Answer 11

Waves will pass through transparent material. It still can refract, but the process of passing through the material and still emerging is transmission.

Question 12

What is absorption of waves?

Answer 12

If the frequency of light matches the energy levels of the electrons, light will be absorbed by the electrons and not reemitted, and over time reemitted as heat. So that frequency has been absorbed.

Question 13

What happens when sound travels through the ear? (4)

Answer 13

1. Sound waves travel inside the ear canal, and travel to the ear drum (a thin membrane), where the waves vibrate .
2. The sound waves reach the tiny bones where vibrations amplify.
3. Vibrations are then passed to the liquid inside the cochlea. Tiny hairs inside the cochlea detect these vibrations and create electrical signals called impulses.
4. Impulses travel along neurones in the auditory nerve to reach the brain.

Question 14

Describe the term “ultrasound”

Answer 14

This is a sound wave with a higher frequency than 20,000 Hz.

Question 15

What are some uses for ultrasound? (2)

Answer 15

1. Sonar - Pulse of ultrasound is sent below a ship, and the time taken for it to reflect and reach the ship can be used to calculate the depth.
2. Foetal scanning – Used to create an image of the foetus. Ultrasound waves partially reflect at each surface boundary, and bounce back by echoes. By measuring the time, it takes for these echoes to return, an image can be produced.

Question 16

Describe the term “infrasound”

Answer 16

This is a sound wave with a frequency lower than 20Hz – also known as seismic waves- there are two P and S waves and they are used to explore the earths core.

Question 17

What are P and S waves?

Answer 17

P waves are longitudinal and can pass through solids and liquids.
S waves are transverse, only passing through solids(these move slower too).