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Physics > Topic 6 - Waves > Flashcards

Topic 6 - Waves Flashcards

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1
Q

Describe transverse waves

A

The vibrations are perpendicular to the direction of energy transfer
e.g water waves

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2
Q

Describe longitudinal

A

The vibrations are parallel to the direction of energy transfer
e.g sound waves

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3
Q

Define time period

A

the time taken for a particle to complete one vibrational cycle

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4
Q

Define frequency

A

the number of complete waves every second (measured in hertz)

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5
Q

Time period =

A

1 / frequency

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6
Q

Define wave speed

A

the speed at which energy is being transferred

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7
Q

Wave speed =

A

frequency x wavelength

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8
Q

Describe how you would use a ripple tank to measure the speed of waves

A
  • set up the ripple tank, put a large sheet of card under the tank on the floor and pour about 5mm of water into the tank
  • put the wooden rod so it just touches the surface of the water
  • switch on the overhead lamp and motor and adjust so the waves are low frequency and you can see it clearly on the card
  • place a meter ruler on the card, measure across as many waves as possible and divide that length by the number of waves (gives the wavelength)
  • count the number of waves passing a point in 10 seconds and divide by 10 (gives the frequency)
  • calculate wave speed using wave speed = frequency x wavelength
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9
Q

Describe how you would calculate the wave speed on an elastic cord

A
  • set up a vibration generator, power supply, elastic cord, masses and a hanger, a wooden bridge and pulley on a clamp
  • turn on the vibration generator
  • use a meter ruler to measure as many half wavelengths as possible, then divide total length by the number of half waves then times by 2 (gives the wavelength)
  • frequency is the frequency of the power supply
  • use wave speed = frequency x wavelength
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10
Q

What is the law of reflection?

A

angle of incidence = angle of reflection

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11
Q

What 3 things could happen when a wave arrives at an interface (boundary between 2 mediums)?

A
  • absorbed
  • transmitted (continue travelling)
  • reflected
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12
Q

Describe the angle of incidence

A

the angle between the incoming ray and the normal

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13
Q

Describe the angle of reflection

A

the angle between the reflected ray and the normal

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14
Q

Reflection produces a _____ image.

A

virtual

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15
Q

What is specular reflection?

A
  • happens when a wave is reflected in a single direction by a smooth surface
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16
Q

What is diffuse reflection?

A
  • happens when a wave is reflected by a rough surface and the reflected rays are scattered in lots of directions
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17
Q

What is refraction?

A

when light passes from one medium to another with a different optical density, the light changes direction

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18
Q

Describe how to investigate refraction

A
  • place a transparent rectangular block on a piece of paper and trace around it
  • use a ray box to shine a ray of light in the middle of one side of the block and trace the incident ray and emerging ray
  • remove block and join up the lines to show the path of the refracted ray
  • draw the normal where the light ray entered the block and use a protractor to measure the angle of incidence and the angle of refraction
  • repeat experiment with different materials of block
19
Q

Describe how to investigate reflection

A
  • draw a straight line on a piece of paper and place an object so its side lines up
  • shine a ray of light at the object and trace the incoming and reflected light beams
  • draw the normal where the ray hits the object
  • use a protractor to measure the angle of incidence and reflection, and make note of the width and brightness of the reflected ray
  • repeat with different objects
20
Q

Define electromagnetic waves

A

Transverse waves that transfer energy from the source of the waves to an absorber

21
Q

All electromagnetic waves are …

A
  • transverse
  • can travel through a vacuum
  • all travel at the same speed in a vacuum
22
Q

Name the 7 types of electromagnetic waves, starting with the low energy

A
  • radio waves
  • microwaves
  • infrared
  • visible light
  • ultraviolet
  • x-rays
  • gamma rays
23
Q

Describe the red end of the EM spectrum

A
  • lower energy
  • long wavelength
  • low frequency
24
Q

Describe the violet end of the EM spectrum

A
  • higher energy
  • short wavelength
  • high frequency
25
Q

What are radio waves use and why?

A
  • used for long-range communication
  • because they can be reflected from the Earth’s atmosphere
26
Q

What are microwaves use and why?

A
  • satellite communications
  • because microwaves can penetrate Earth’s atmosphere
27
Q

What are infrared use and why?

A
  • optical fibre communication
  • because they can undergo total internal reflection
28
Q

What is visible light use and why?

A
  • taking photos and videos ( and seeing)
  • cameras are set up to detect visible light
29
Q

What is ultraviolet use and why?

A
  • for detecting security ink ( and suntan)
  • because it fluoresces with ultraviolet lighting
30
Q

What is X-Rays use and why?

A
  • to photograph bones
  • because X-Rays can penetrate soft tissues but not bones
31
Q

What is gamma rays use and why?

A
  • to sterilise medical tools
  • because gamma kills bacteria
32
Q

What is the danger of microwaves?

A

high intensity microwaves can cause heating of internal organs

33
Q

What is the danger of gamma, x-rays and high intensity UV?

A
  • can harm cells and cause cancer
  • because they are highly ionising
34
Q

Describe the colour black as an absorber/emitter

A

good absorber
good emitter

35
Q

Describe the colour dull/dark as an absorber/ emitter

A

reasonable absorber
reasonable absorber

36
Q

Describe white as an absorber/emitter

A

poor absorber
poor emitter

37
Q

Describe silver as an absorber/emitter

A

very poor absorber
very poor emitter

38
Q

If a material is a poor absorber, it will be a good …

A

reflector

39
Q

Describe the practical investigating infrared radiation using colour

A
  • set up four identical flasks painted black, grey, white and silver
  • fill the flasks with hot water, ensuring the measurements start from the same initial temperature
  • note the starting temperature, then measure the temperatures at regular intervals
  • plot the results on a graph
40
Q

All warm objects emit thermal radiation in the form of ………..

A

infrared waves

41
Q

Define a perfect black body

A

An object that absorbs all of the radiation that hits it and does not reflect/transmit any radiation

42
Q

What are the 3 sets of words you use to describe an image?

A
  • magnified (bigger) or diminished (smaller)
  • inverted (upside down) or upright
  • real (on the opposite side of the lens) or virtual (on the same side of the lens)
43
Q

What do filters do?

A

Filters absorb every colour but one, which they transmit.

44
Q
A

Physics (8 decks)

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