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physics > waves > Flashcards

waves Flashcards

1
Q

What is wavelength?

A

distance from one peak to the next (or trough)

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2
Q

What is frequency and what is it measured in?

A

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

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3
Q

What is amplitude?

A

height of a wave (rest to crest)

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4
Q

What is the period?

A

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

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5
Q

What is the equation linking speed, frequency and wavelength?

A

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

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6
Q

What are transverse waves?

A

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

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7
Q

Give examples of transverse waves (4)

A
  • light, all other EM waves
  • slinky spring (up and down)
  • waves on strings
  • ripples on water
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8
Q

What are longitudinal waves?

A

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

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9
Q

Give examples of longitudinal waves (3)

A
  • sound + ultrasound
  • shockwaves
  • slinky spring (push end)
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10
Q

What do waves transfer?

A

energy in direction they travel – without transferring matter

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11
Q

What is a wavefront?

A

imaginary surface representing corresponding points of a wave that vibrate together

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12
Q

What is the distance in each wavefront equal to?

A

one wavelength

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13
Q

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

A
  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
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14
Q

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

A

higher frequency, shorter wavelength

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14
Q

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

A

lower frequency, longer wavelength

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15
Q

What is the Doppler effect?

A

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

16
Q

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

A
  1. radio waves
  2. microwaves
  3. infrared waves
  4. visible light
  5. ultraviolet
  6. x-rays
  7. gamma rays
16
Q

How does the Doppler effect work? (4)

A
  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
17
Q

Which EM wave has the highest frequency and lowest wavelength?

A

gamma rays

18
Q

Which EM wave has the lowest frequency and highest wavelength?

A

radio waves

19
Q

Which colour has the longest wavelength?

A

red

20
Q

Which colour has the lowest frequency?

A

violet

21
Q

What are the uses of microwaves? (2)

A
  • communication: mobile phone signals, satellite and TV
  • cooking, heating food, waves absorbed by water molecules in food
21
Q

What are the uses of radio waves? (3)

A
  • produced or can induce oscillations in electrical circuits
  • carry TV, radio, mobile phone signals
  • connect printers, Bluetooth devices to computer or laptop
22
Q

What are the uses of infrared radiation? (4)

A
  • 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
23
Q

What are the uses of ultraviolet waves? (3)

A
  • 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
24
Q

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

A
  • 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)
25
Q

What is visible light used for?

A

photography

26
Q

When is EM radiation dangerous?

A

the higher the frequency

27
Q

What are the uses of gamma rays? (2)

A
  • sterilises medical equipment and food
  • kills cancer cells from radioactive source
28
Q

Why is EM radiation dangerous?

A

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

29
Q

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

A

heat human body tissue > use shielding in microwave ovens

30
Q

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

A

causes skin burns > use insulating materials

31
Q

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

A
  • damage surface cells = blindness
  • cell mutation or destruction
  • ionising
    > wear sunscreen
32
Q

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

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

physics (6 decks)

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