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GCSE Physics > 5) Light & The Electromagnetic Spectrum > Flashcards

5) Light & The Electromagnetic Spectrum Flashcards

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1
Q

What wave type are all electromagnetic waves?

A

Transverse

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2
Q

What speed do all EM waves travel at in a vacuum?

A

The same speed

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3
Q

What are the 7 types of EM wave?

A 
Gamma
X-ray
Ultravoilet
Visible
Infrared
Microwave
Radio waves
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4
Q

Which EM wave carries the most energy?

A

Gamma rays

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5
Q

How do gamma rays’ wavelength and frequency compare to the other EM waves?

A

Shortest wavelength

Highest frequency

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6
Q

How do radio waves’ wavelength and frequency compare to the other EM waves?

A

Longest wavelength

Lowest frequency

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7
Q

What happens to the freqquency as wavelength increases?

A

Frequency decreases

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8
Q

What are uses of gamam rays?

A

Medical imaging and therapy
Astronomy
Sterilisation
Food preservation

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9
Q

What are risks of gamma rays?

A

Extremely penetrating and damaging to living tissues and cells

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10
Q

What do we use gamma rays to destroy?

A

Bacteria

Tumours

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11
Q

What are uses of x-rays?

A

Medical and industrial imaging
Treating cancer
Security purposes

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12
Q

Why are x-rays used to scan the body?

A

X-rays penetrate soft materials (body tissue)

Bones are dense and absorb x-rays

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13
Q

What are risks of x-rays?

A

Highly ionising (can damage body cells)

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14
Q

How can you shield yourself from x-rays?

A

Place metals or lead between yourself and the x-rays

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15
Q

What are risks of ultraviolet light?

A

Skin burns
Skin cancer
Cataract formations in the eye

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16
Q

What are uses of ultraviolet light?

A 
Medical and forensic photography
Air purification
Water disinfection
Medical therapy
Detecting fake notes
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17
Q

What do UV photons do to atoms?

A

They give energy to atoms causing them to release visible light

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18
Q

What are risks of infra-red radiation?

A

Serious skin burns if emitted from high intensity sources

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19
Q

What do infra-red lights do to food?

A

Excite the particles causing an increase in temperature

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20
Q

What are uses of infra-red light?

A

TV controls
Security purposes
Body heat detectors

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21
Q

What are uses of microwaves?

A

Satellite communications
Phone signals
Heating food and drink

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22
Q

Why are microwave used for satellite communications?

A

They have a high enough frequency to penetrate the Earth’s atmosphere
Travel in straight lines

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23
Q

What are risks of microwaves?

A

Humans are made up of water so exposure could be harmful

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24
Q

How do we use safety with microwaves?

A

Using protective shielding

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25
Q

What molecules can microwaves transfer energy to?

A

Water molecules

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26
Q

What are risks of radio waves?

A

High intensities can cause internal heating of tissue

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27
Q

What are uses of radio waves?

A

Radio and TV communications

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28
Q

What does radio waves’ long wavelength mean?

A

They can be transmitted around the Earth’s surface and buildings without interference

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29
Q

How can electromagnetic waves be produced?

A

Electrical circuits

Changes in atoms

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30
Q

What do changes in atoms produce?

A

Radiation of lots of different frequencies

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31
Q

How are EM waves produced in electrical circuits?

A

Oscillations can produce radio waves

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32
Q

What happens when radio waves are absorbed?

A

They can create an AC current with the same frequency as the radio wave itself
This means radio waves can lead to oscillations in an electrical circuit

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33
Q

How are EM waves produced in changes in atoms?

A

Changes in the nuclei can result in EM waves being generated or absorbed over a wide frequency range

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34
Q

Where do gamma rays originate from?

A

Changes in the nucelus of an atom

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35
Q

What are the 7 colours of the visible light spectrum?

A 
Red
Orange
Yellow
Green
Blue
Indigo
Violet
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36
Q

Why can we use visible light in optical fibres?

A

It can be totally internally reflected

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37
Q

What are uses of visible light?

A

We use visible light to see the world

Fibre optics

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38
Q

What determines the opacity of an object?

A

Whether light is absorbed, reflected or transmitted

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39
Q

What are the 3 opacities?

A

Opaque
Translucent
Transparent

40
Q

What happens to light to make objects translucent?

A

Light is transmitted but rays are scattered

41
Q

What happens to light to make objects opaque?

A

Light is either reflected or absorbed

42
Q

What happens to light to make objects transparent?

A

Light is transmitted without scattering rays

43
Q

Which colour has the lowest frequency and longest wavelength?

A

Red

44
Q

Which colour has the highest frequency and shortest wavelength?

A

Violet

45
Q

What are the two ways light can be reflected?

A

Diffuse

Specular

46
Q

What is diffuse reflection?

A

When light is scattered by a rough surface

47
Q

What is specular reflection?

A

Light is reflected in a single direction by a smooth surface

48
Q

What is the colour of an opaque object when all of the wavelengths are reflected equally?

A

White

49
Q

What is the colour of an opaque object when all of the wavelengths are absorbed?

A

Black

50
Q

What happens to wavelengths when an object has a particular colour?

A

It reflects all of the particular wavelength (colour)

Absorbs all other wavelengths

51
Q

What do colour filters do?

A

Absorb certain wavelengths and transmit other wavelengths

52
Q

What is internal reflection?

A

When light speeds up when entering a less optically dense medium
Some light is refracted and some light is reflected

53
Q

What happens if the angle of incidence is the same as the critical angle?

A

Light will travel along the boundary of the 2 mediums

54
Q

What is total internal reflection?

A

If the angle of incidence exceeds the critical angle all of the light will be reflected

55
Q

How does a lens form an image?

A

By refracting light

56
Q

What are the main types of lens?

A

Converging (convex)

Diverging (concave)

57
Q

How does the power of a lens increase?

A

When the difference between the middle thickness and edge thickness increases

58
Q

How does a convex lens’ power increase?

A

Thicker middle comapred to edges

59
Q

How does a converge lens’ power increase?

A

Thinner middle compared to edges

60
Q

What is the equation for power of a lens?

A 
P = 1 / f
Power = 1 / focal length
61
Q

How does the focal length size affect the power?

A

Larger focal length = lower power

62
Q

What is the focal length?

A

The distance between the lens and the principle focus

63
Q

How does a lens form an image?

A

By refracting light

64
Q

What does a convex lens look like?

A

Wider in middle than edges

65
Q

Where is the principal focus of a convex lens?

A

Where all rays hitting the lens parallel to the axis meet

66
Q

What does a converge lens look like?

A

Wider edges than middle

67
Q

What happens when parallel light rays enter a concave lens?

A

They disperse

68
Q

Where is the principal focus of a concave lens?

A

Tracing back along the path of the dspersed rays, they will come from the principal focus behind the lens

69
Q

What type of images can convex lenses produce?

A

Real or virtual

70
Q

Whattype of images can concave lenses produce

A

Only virtual

71
Q

What is the equation to calculate the magnification a lens produces?

A

Magnification = image height / object height

72
Q

What is the unit for magnification?

A

It is a ratio

No units

73
Q

What can we not project onto a screen?

A

Virtual images

74
Q

Where does a virtual image appear?

A

On the same side of the lens to the object

75
Q

Where does a real image appear?

A

On the other side of the lens to the object

76
Q

How do you draw ray diagrams?

A

1) Draw the principal axis (horizontal line straight through middle of lens)
2) Use correct lens symbols
3) Mark princiapl focus on either side of the lens, draw on dot on principal axis and label it F
4) Mark position of the object as an arrow standing on principal axis
5) Draw light rays

77
Q

What is the symbol for convex lenses in ray diagrams?

A

Double headed arrow

78
Q

What is the symbol for concave lenses in ray diagrams?

A

Inverted double headed arrow

79
Q

How do you draw a convex lens ray diagram?

A

1) Draw line from top of object to lens
2) From point on lens draw second line through principal focus on other lens side
3) Draw third line from top of object straight through mid of lens
4) If lines meet on other lens side this forms a real image
5) Draw image as a vertical arrow connecting the point lines meet to principal axis
6) If lines do not meet this forms a virtual image

80
Q

What do all objects emit?

A

Radiation

81
Q

Where will an object always transmit heat to?

A

Hotter area to colder area

82
Q

When is the rate of temperature emission higher?

A

When an object’s internal temperature is higher than the environment’s temperature

83
Q

What does a body at constant temperature do with radiation?

A

Absorbs radiation at the same rate it emits radiation

84
Q

What is the process of the greenhouse effect?

A

1) Sun emits short wavelength infrared radiation
2) Earth absorbs some radiation but long wavelength is reflected
3) Greenhouse gases can’t absorb frequency emitted by sun but can absorb longer wavelength radiation
4) Gases re-radiate energy towards Earth
5) Earth’s temperature increases

85
Q

What length wavelengths does the sun emit?

A

Short wavelength infrared radiation

86
Q

What length wavelength does the Earth reflect?

A

Long wavelength radiation

87
Q

What are 3 types of greenhouse gases?

A

Methane
Carbon dioxide
Water vapour

88
Q

What does the temperature of a body (object) depend on?

A

Rate of absorbtion and rate of emission of radiation

89
Q

What factors affect the rate of emission and absorbtion?

A

Surface area
External temperature
Internal temperature

90
Q

How much solar energy per square metre falls on Earth?

A

340 Watts

91
Q

What percentage of solar energy is reflcted to space?

A

29%

92
Q

What percentage fo solar energy is absorbed in the atmosphere?

A

23%

93
Q

What percentage of solar energy is absorbed at the surface?

A

48%

94
Q

Why can infra-red radiation travel through space?

A

It does not need a medium

95
Q

What can be said about the amount of energy absorbed and emitted by the sun?

A

It is in balance

GCSE Physics (14 decks)

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