waves

Question 1

What is wavelength?

Answer 1

distance from one peak to the next (or trough)

Question 2

What is frequency and what is it measured in?

Answer 2

how many complete waves there are per second and Hertz (Hz)

Question 3

What is amplitude?

Answer 3

height of a wave (rest to crest)

Question 4

What is the period?

Answer 4

time it takes in seconds for one complete wave to pass a point

Question 5

What is the equation linking speed, frequency and wavelength?

Answer 5

speed (m/s) = frequency (Hz) x wavelength (m)

Question 6

What are transverse waves?

Answer 6

waves in which the vibrations are perpendicular to the direction of energy transfer

Question 7

Give examples of transverse waves (4)

Answer 7

• light, all other EM waves
• slinky spring (up and down)
• waves on strings
• ripples on water

Question 8

What are longitudinal waves?

Answer 8

waves in which the vibrations are parallel to the direction of energy transfer

Question 9

Give examples of longitudinal waves (3)

Answer 9

• sound + ultrasound
• shockwaves
• slinky spring (push end)

Question 10

What do waves transfer?

Answer 10

energy in direction they travel – without transferring matter

Question 11

What is a wavefront?

Answer 11

imaginary surface representing corresponding points of a wave that vibrate together

Question 12

What is the distance in each wavefront equal to?

Answer 12

one wavelength

Question 13

Why do waves have different wavelengths when an observer is farther, moving towards, or stationary from them? (2)

Answer 13

1. wave speed is constant, so if the source is moving, it follows the waves in front of it
2. this causes the wavefronts to bunch up in front of the moving source and spread out behind it

Question 14

What is the frequency when a wave is moving towards you?

Answer 14

higher frequency, shorter wavelength

Question 14

What is the frequency when a wave is moving away from you?

Answer 14

lower frequency, longer wavelength

Question 15

What is the Doppler effect?

Answer 15

the apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer

Question 16

Put the EM waves in order from the highest wavelength to the lowest wavelength

Answer 16

1. radio waves
2. microwaves
3. infrared waves
4. visible light
5. ultraviolet
6. x-rays
7. gamma rays

Question 16

How does the Doppler effect work? (4)

Answer 16

1. the waves produced by a source which is moving towards or away from an observer will have a different wavelength than they would if the source were stationary
2. this is because the wave speed is constant, so if the source is moving, it ‘catches up’ to the waves in front of it. this causes the wavefronts to bunch up in front of the moving source and spread out behind it
3. the frequency of a wave from a source moving towards you will be higher and its wavelength will be shorter than the wave produced by the source
4. the frequency of a wave from a source moving away from you will be lower and its wavelength will be longer than the wave produced by the source

Question 17

Which EM wave has the highest frequency and lowest wavelength?

Answer 17

gamma rays

Question 18

Which EM wave has the lowest frequency and highest wavelength?

Answer 18

radio waves

Question 19

Which colour has the longest wavelength?

Answer 19

red

Question 20

Which colour has the lowest frequency?

Answer 20

violet

Question 21

What are the uses of microwaves? (2)

Answer 21

• communication: mobile phone signals, satellite and TV
• cooking, heating food, waves absorbed by water molecules in food

Question 21

What are the uses of radio waves? (3)

Answer 21

• produced or can induce oscillations in electrical circuits
• carry TV, radio, mobile phone signals
• connect printers, Bluetooth devices to computer or laptop

Question 22

What are the uses of infrared radiation? (4)

Answer 22

- all objects emit infrared radiation: hotter the object = more infrared radiation emits - remote control for TV + video games - electric heaters + cookers - thermal cameras + optical fibres in cable TV and high-speed broadband

Question 23

What are the uses of ultraviolet waves? (3)

Answer 23

- some chemicals emit light when they absorb ultraviolet light - fluorescent chemicals used to make posters, inks, security pen markers - tanning salons: use UV lamps to give an artificial tan

Question 24

What are the uses of X-ray waves? (3)

Answer 24

- detects internal cracks in metal objects - produces images of broken bones - destroy cancerous tumours using high energy x-rays (short wavelength compared to those used in x-ray imaging)

Question 25

What is visible light used for?

Answer 25

photography

Question 26

When is EM radiation dangerous?

Answer 26

the higher the frequency

Question 27

What are the uses of gamma rays? (2)

Answer 27

- sterilises medical equipment and food - kills cancer cells from radioactive source

Question 28

Why is EM radiation dangerous?

Answer 28

EM radiations can enter living tissue, causing the heating of cells

Question 29

What are the dangers of microwaves and how can we prevent them?

Answer 29

heat human body tissue > use shielding in microwave ovens

Question 30

What are the dangers of infrared radiation and how can we prevent them?

Answer 30

causes skin burns > use insulating materials

Question 31

What are the dangers of ultraviolet waves and how can we prevent them? (4)

Answer 31

- damage surface cells = blindness - cell mutation or destruction - ionising > wear sunscreen

Question 32

What are the dangers of gamma rays and how can we prevent them? (4)

Answer 32

- ionising - cell mutation or destruction - tissue damage or cancer > short exposure time