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GCSE Physics Paper 2 > Waves > Flashcards

Waves Flashcards

1
Q

How do waves transfer energy?

A

When waves travel through a medium the particles of the medium oscillate and transfer energy between each other.

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2
Q

What is the amplitude of a wave?

A

This is the maximum displacement of a point on the from its undisturbed position

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3
Q

What is wavelength?

A

This is the distance between the same point on two adjacent waves

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4
Q

What is the frequency of wave?

A

This is the number of complete waves passing a certain point per second it is measured in Hertz, Hz

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5
Q

How do you find the period of a wave?

A

This is the amount of time it takes for a full cycle of the wave
T=1/f
Period = 1/frequency

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6
Q

What is a transverse wave?

A

This is where the oscillations are perpendicular to the direction of energy transfer.

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7
Q

What is a longitudinal wave?

A

This is where the oscillations are parallel to the direction of energy transfer

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8
Q

Give some examples of a transverse wave

A

All electromagnetic waves
Ripples and waves in water
A wave on a string

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9
Q

Give some examples of a longitudinal wave

A

Sound waves in air, ultrasound

Shock waves - seismic waves

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10
Q

What is wave speed?

A

This is the speed at which energy is being transferred

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11
Q

What is the equation for wave speed?

A

Wave speed=frequency*wavelength

v=f*wavelength

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12
Q

How would you measure waves?

A

Oscilloscope
Water ripples
Strings

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13
Q

How would you measure sound waves?

A

Set up two microphones and an oscilloscope to find the wavelength of the sound waves generated. Slowly move one microphone away until the two waves are aligned on the display. Measure the distance between the microphones to find one wavelength. Then use the formula V=f*wavelength to find speed. The frequency is whatever you set the signal generator to.

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14
Q

How would you measure the speed of water ripples?

A

Use a signal generator attached to a dipper of a ripple tank you can create waves at a set frequency. Use the lamp to see the water ripple below the tank. Measure the distance between the shadow lines from a picture that are ten wavelengths apart then divide this by ten to find the average. Use V=f*wavelength.

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15
Q

How would you find wave speed of a string?

A

Use a generator and vibration transducer to keep a steady wave to form on the string. Measure the wavelength of these waves through a photo measure four or five half wave lengths then divide by that number then double it. Use the wave speed equation.

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16
Q

Give some properties of waves

A

Waves can be absorbed, transmitted or reflected, when a wave arrives at a boundary.

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17
Q

What is the simple rule of reflected waves?

A

Angle of incidence=angle of reflection

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18
Q

What is diffuse reflection?

A

This is where a wave is reflected by a rough surface and the reflected waves are scattered in lots of different directions. When light is reflected by a rough surface the surface appears matte and you don’t get a clear reflection/ image of objects.

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19
Q

What are electro-magnetic waves?

A

They are transverse waves that transfer energy from a source to an absorber. All EM waves travel at the same speed through air or a vacuum.

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20
Q

What are the forms of EM waves?

A 
Radio waves
Micro waves
Infra red waves
Visible light waves
Ultra voilet
X-rays
Gamma rays
They each have different frequencies and properties so they are used differently.
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21
Q

What is refraction?

A

This is where the wave changes direction when it crosses a boundary. The angle at which it is refracted depends on how much the wave speeds up or slows down which usually depends on the density of the two materials. When the wave slows it bends towards the normal and when it speeds up it bends away from the normal.

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22
Q

What are EM waves made up of?

A

Oscillating electric and magnetic fields. Alternating current are made up of oscillating charges.

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23
Q

What are the uses of radio waves?

A

They are used for communication, This is because long wavelengths diffract around curved surfaces. This makes it possible to receive the wave even if you cannot see the transmitter. However, short radio waves can also be received at long distances due to them being reflected from the ionosphere - an electrically charged layer in the Earths upper atmosphere.

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24
Q

What are micro wave rays used for?

A
  • They are used in ovens, the microwaves need to be absorbed by water molecules. The microwaves penetrate a few centimetres into the food before being absorbed and transferring the energy they are carrying causing the water to heat up.
  • They are also used for communicating with satellites in space because microwaves can pass through the earths atmosphere without being reflected or refracted.
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25
Q

What is infra red waves used for?

A

They are used to increase and monitor temperature. The hotter the object the more infra red radiation is given off.
They are used in toasters heating element.

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26
Q

How does a fibre optic cable work?

A

They are thin glass or plastic fibres that can carry data over long distances as pulses of visible light. They work because of reflection, the light rays are bounced back and forth until they reach the end of the fibre.

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27
Q

What are some uses for ultraviolet rays?

A
  • Fluorescent colour.
  • Fluorescent lights
  • Security devices, some things invisible will show under the light
  • It can be used to get a suntan,
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28
Q

What are X-rays used for?

A

They are used to take photographs of you’re bones to see if there is and breaks or fractures.

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29
Q

How do x-rays work?

A

The x-rays pass through flesh easily but not so easily through dense materials such as bone or metal - the amount of radiation that’s absorbed gives you an x-ray image.

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30
Q

How are gamma rays used in treating cancer patients?

A

High doses of these rays and x-rays means living cells will die - so they are carefully directed to cancer cells in small amounts which focus on the cancer cells, avoiding healthy tissue (radiotherapy).

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31
Q

What are the other uses for gamma rays (besides radiotherapy)?

A

It can be used for medical tracers this is where the gamma emitting source is injected into the patient, and its progress is followed around the body. It can pass through the body to be detected.

32
Q

What are the precautions that radiographers have to take?

A

Due to the constant exposure of gamma and x-rays they have to limit there exposure so they do not develop health illness’s for example they will wear a lead apron or leave the room.

33
Q

What happens when EM waves enter you’re body?

A

The effects depends on how much energy the wave transfers. Cells that have a high frequency damage cells which can cause skin to age prematurely, blindness, cancer, sunburn - UV radiation.
Ionising radiation can cause gene mutation or cell destruction and cancer - x-rays and gamma rays.

34
Q

What is the risk in using UV rays?

A
  • They increase the risk of skin cancer,

- Cause premature skin ageing.

35
Q

What is a convex lens?

A
  • Thicker in the centre than at the edges,

- It focuses light/ converges light rays.

36
Q

Why does the light ray in the middle of the convex lens not bend?

A
  • It is directly along the normal/ principal axis or the centre of the lens.
37
Q

What is the principle focus?

A

The point where all the light rays focus (F).

38
Q

What is the focal length?

A

The distance between the centre of the lens and the principal focus.

39
Q

Can the focal length differ between convex lens?

A

Ye, different strength lens’ have different focal lengths (thicker or thinner lenses.)

40
Q

How do you draw a ray diagram for a convex lens?

A
  • First place an object behind the lens,
  • Then draw a line from the top of the object straight through the centre of the convex lens,
  • Then draw a line from the top of the object, a horizontal line to the lens,
  • This line (represent light ray), is refracted and another line is drawn that goes through the principal focus,
  • Where the two lines meet (first one and last one) shows you the top of the image,
  • You can calculate the new size of the image by comparing heights of the original image and the new image, if it shrinks it diminished, if it gets bigger it has magnified,
  • If the image is below the principal axis, it is inverted (upside down),
  • A real image is an image formed (light converges) after the lens, an Virtual image forms behind the lens.
41
Q

What is a real image and an Virtual image?

A

Real:
- When the light rays converge after the lens, you could put a screen there and the image would show,
Virtual:
- The light does not converge, but if you trace the straight lines back, the light will converge somewhere before the lens.

42
Q

What are the properties of the image (ray diagram) if the object is place more than 2 focal lengths from the lens?

A
  • Diminished (shrunk),
  • Inverted (upside down),
  • Real (light converged)
43
Q

What are the properties of the image (ray diagram) if the object is placed in between 2 and 1 the focal lengths from the lens?

A
  • Magnetised (enlarged),
  • Inverted,
  • Real
44
Q

What do the properties of an image depend on?

A

The distance between the object and the lens.

45
Q

What is the symbol for a convex lens?

A

An arrow with two heads.

but vertical.

46
Q

What is a concave lens?

A
  • Thicker on the edges than the centre,

- Diverges light rays.

47
Q

What is the symbol for a concave lens?

A

A two headed arrow, but the arrows point into the line instead of away.
>-< but vertical.

48
Q

Where is the principal focus of a concave lens?

A
  • Before the lens,
  • Since the light rays diverge, you can trace the light rays back to where they all meet, this is the focal point.
  • This is not where all the light actually comes from, it just appears to be that way because the diverged light focuses behind the lens, light is actually coming from all directions into the lens.
49
Q

How do you draw a ray diagram for a concave lens?

A
  • First place an object behind the lens,
  • Then draw a line from the top of the object straight through the centre of the convex lens,
  • Then draw a line from the top of the object, a horizontal line to the lens,
  • This line (represent light ray), is refracted and another line is drawn, this line is drawn from the principal focus before the lens and passes through the lens in a straight line.
  • Where the two lines meet (first one and last one) shows you the top of the image,
  • You can calculate the new size of the image by comparing heights of the original image and the new image, if it shrinks it diminished, if it gets bigger it has magnified,
  • If the image is below the principal axis, it is inverted (upside down),
  • A real image is an image formed (light converges) after the lens, a virtual image forms behind the lens.
50
Q

What are the properties of an image formed using a concave lens?

A
  • Diminished,
  • Right way up,
  • Virtual.
51
Q

What is the ray diagram for a magnifying glass?

A
  • The object must be placed before the focal length of the lens,
  • Draw the second horizontal line, in line with the top of the object and meeting the lens,
  • Its refracted line should go through the principal focal on the other side of the lens,
  • The two lines never meet after the lens because they are diverging,
  • So you must trace back the lines using dotted lines. where they meet before the lens,
  • Where the lines meet is the position of the image.
52
Q

What are the properties of the image if the object is before the principal focus?

A
  • Magnified,
  • Right way up,
  • Virtual
53
Q

What is the equation for magnification?

A

Magnification = image height/ object height.

54
Q

What is secular reflection and where does it take place?

A
  • When all the light rays are reflected in a singular direction,
  • This takes place on smooth surfaces like a mirror.
55
Q

What is white light made of?

A

All colours of light on the spectrum.

56
Q

What is the light spectrum?

A 
Red
Orange
Yellow
Green
Blue
Indigo
Violet.
57
Q

What determines the colour of an object?

A

Depends on which wavelengths of light are reflected, transmitted or absorbed

58
Q

What makes all colours different and why do we see them differently?

A

Each colour has a band of wavelength and frequency,

When our eyes sees a colour, it knows which one it is by the wavelength and frequencies..

59
Q

How do colour filters work?

A

They absorb all the colours of visible light besides it own, it transmits its own colour through the filter.

60
Q

What is a translucent object?

A
  • They allow some light to pass through, the light rays scatter so we cannot see them clearly.
61
Q

What is an opaque object?

A

Does not allow any light to pass through so we cannot see through them.

62
Q

Why is a black object black?

A

It absorbs all light.

63
Q

Why is a white object white?

A

It reflects all light.

64
Q

Why is a red object red?

A

It absorbs all light besides red, which it reflects.

65
Q

What colour will a green object appear thorough a red filter?

A

Black, the red light is let through the filter, but the green object absorbs the red light.

66
Q

What is a perfect black body?

A

An object that absorb all radiation, no radiation is reflected and no radiation is transmitted (allowed through).
It will also be the best possible radiation emitter.

67
Q

Do all objects emit and and absorb infrared radiation?

A

Yes. No matter the temperature, however, a hotter object will emit more infrared radiation in a given time, compared than a cooler object.

68
Q

What do wavelength and intensity of radiation depend on?

A

The temperature of an object.

  • The higher the temperature of an object, the shorter the wavelength of radiation it emits.
  • The intensity of the radiation also increases at higher temperatures.
69
Q

Why do very hot objects produce visible light?

A

Since the temperature is high, the object will release short wavelength radiation, so short that i is visible light.

70
Q

What happens if an object is hotter than its surroundings (in terms of radiation emission)?

A

It will emit more radiation than it absorbs, so its temperature will decrease.

71
Q

What happens if an object is cooler than its surroundings (in terms of radiation emission)?

A

It will absorb more radiation that it emits, so its temperature will increase.

72
Q

What happens if an object is at a constant temperature?

A

The object is emitting and absorbing radiation at the same rate.

73
Q

What is the only way the Earth can gain or lose energy?

A

Absorbing or emitting radiation back into space.

74
Q

What kind of radiation does the sun emit?

A

Short wavelength radiation:

Visible light, ultraviolet and infrared.

75
Q

Why do cloudy nights tend to be warmer than clear nights?

A
  • The clouds reflect the infrared radiation back down to earth and prevent it from being radiated back into space.

GCSE Physics Paper 2 (5 decks)

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