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Physics⚡️ > Chapter 13 > Flashcards

Chapter 13 Flashcards

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1
Q

why do different types of each wave have different effects?

A

the energy they transfer depends on the wavelength of the waves

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2
Q

what are the 7 waves?

A 
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays 
Gamma rays
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3
Q

wavelength of radio waves

A

between 1m and 1 x 10^4 metres

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4
Q

what type of waves are electromagnetic waves?

A

transverse

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5
Q

what do EM waves do?

A

transfer energy from a source to an absorber

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6
Q

wavelength of microwaves

A

10^-2 metres

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7
Q

wavelength of infrared

A

10^-5 metres

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8
Q

wavelength of visible light

A

10^-7 metres

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9
Q

wavelength of ultraviolet

A

10^-8 metres

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10
Q

wavelength of x rays

A

10^-10 metres

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11
Q

wavelength of gamma rays

A

10^-15 metres

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12
Q

what happens to the wavelength as you go down the spectrum (from radio waves to gamma rays)

A

decreases

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13
Q

what happens to the frequency as you go down the spectrum (from radio waves to gamma rays)?

A

increases

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14
Q

why is there such a range of wavelengths in the EM spectrum?

A

the waves are generated by a variety of changes in atoms and atomic nuclei

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15
Q

how fast do all EM waves travel in a vacuum or in space?

A

3x10^8 metres/second

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16
Q

equation for wavespeed

A

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

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17
Q

what is white light?

A

light that comes from the sun and ordinary lamps

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18
Q

which colour has the longest wavelength?

A

red

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19
Q

which colour has the shortest wavelength?

A

violet

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20
Q

what do all objects emit?

A

infrared radiation

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21
Q

what happens to the amount of infrared radiation emitted as the object gets hotter?

A

it increases

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22
Q

why is infrared radiation so damaging?

A

it heats up cells to can damage or kill them

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23
Q

why is infrared used in optical fibres?

A

it is absorbed by the glass fibres less than visible light

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24
Q

why are microwaves used in satellite TV and communications?

A

they can pass through Earth’s atmosphere easily to reach satellites and carry mobile phone signals

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25
Q

why are microwaves used in ovens?

A

they penetrate food and are absorbed by the water molecules, transferring their energy and heating it

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26
Q

how are microwaves used in satellites?

A

they are sent out into space by a transmitter
the satellite picks up the signal and transmits it back to earth in a different direction
where it is received by a satellite dish on the ground

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27
Q

why and how is infrared used in TV remote controls?

A

they are easily produced and received

the controller sends out a series of infrared pulses

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28
Q

how do infrared cameras work?

A

they detect infrared radiation and convert it to an electrical signal, which is displayed on a screen

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29
Q

how do infrared heaters work?

A

a wire emits infrared radiation
it is absorbed by the objects in the room
energy is transferred by the infrared waves to their thermal energy stores and they heat up

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30
Q

uses of microwaves 2

A

communications (satellites)

heating food

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31
Q

properties of microwaves 3

A

absorbed by water molecules
can travel long distances
usually not harmful

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32
Q

uses of infrared 3

A

remote controls
heating
thermal imaging

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33
Q

properties of infrared 2

A

easy and cheap to produce with not much power

can be felt but not seen

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34
Q

uses of radio waves 3

A

mobile phones
radios
TVs

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35
Q

properties of radio waves

A

can travel long distances
low energy
normally not harmful

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36
Q

why can micro and radio waves be dangerous?

A

they can penetrate and heat the body

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37
Q

what are the four carrier waves?

A

radio waves
infrared
visible light
microwaves

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38
Q

what are carrier waves?

A

used to carry a signal

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39
Q

properties of shorter wavelength radio waves? 2

A

carry more information

smaller range

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40
Q

what are fibre optics and how do they work?

A

they are small glass fibres that transmit signals carried by visible light or infrared radiation
the light rays are reflected and can’t escape the fibre

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41
Q

benefits of fibre optic over radio/microwaves? 2

A 
carry more information (shorter wavelength)
more secure (signal can't leave fibre)
42
Q

why are microwaves commonly used with satellites? 2

A

they can travel between the satellite and the ground

they don’t spread out so don’t weaken as much as radio waves do

43
Q

why are radiowaves with short wavelengths used for TV broadcasting from masts?

A

they carry more information s

44
Q

why can long wave radio wavelengths be transmitted and received around the world?

A

the long wavelengths diffract around the curved surface of the earth

45
Q

why can short wave radio wavelengths be transmitted and received around the world?

A

they are reflected from the ionsphere so zigzag around the world to their destination

46
Q

what is the ionsphere?

A

an electrically charged layer in the earth’s upper atmosphere

47
Q

how does Bluetooth work?

A

it uses short wave radio wavelengths to send data over short distances

48
Q

what are electromagnetic waves made from?

A

oscillating electric and magnetic fields

49
Q

what are alternating currents made from

A

oscillating charges

50
Q

what is produced when alternating currents oscillate?

A

electric and magnetic fields (EM waves)

51
Q

why do microwaves heat food faster than normal ovens?

A

the waves penetrate into the food and are directly absorbed by it

52
Q

why don’t ovens absorb microwaves?

A

they don’t contain water molecules

53
Q

uses of infrared radiation 3

A

remote control
night vision
heating

54
Q

properties of infrared?

A

easy and cheap to produce, can be felt but not seen

55
Q

uses of visible light 3

A

seeing
lighting
signalling

56
Q

properties of visible light 2

A

different colours

can reflect and refract

57
Q

uses of ultraviolet 2

A

sun beds

security marking

58
Q

properties of ultraviolet 3

A

3 types: UVA/B/C
can be harmful in large doses
can be seen by insects

59
Q

uses of x rays 2

A

seeing inside body

luggage scanners

60
Q

properties of x rays 3

A

can penetrate thin materials
blocked by dense materials like bones
harmful

61
Q

uses of gamma rays 2

A

treat cancer cells

kill bacteria

62
Q

properties of gamma rays 2

A

highly penetrative

very dangerous - can kill cells

63
Q

what is fluorescence?

A

when certain chemicals absorb ultraviolet rays and emit visible light

64
Q

why are ultraviolet waves harmful to human eyes?

A

they carry more energy than visible light

65
Q

differences between x rays and gamma rays

A

x rays are produced when electrons moving at high speeds are stopped
gamma rays are produced by unstable nuclei releasing electrons

66
Q

what is ionisation?

A

when x rays or gamma rays knock electrons out of an atom, making it charged

67
Q

why is ionising radiation so dangerous?

A

it can ionise and damage healthy body cells

68
Q

why are x and gamma rays used in radiotherapy?

A

they can kill living cells

69
Q

why are gamma rays used as tracers?

A

the gamma rays pass out of the body and can be detected so the source is tracked

70
Q

what is the wavelength of an x ray the same as?

A

the diameter of an atom

71
Q

what is radiation dose?

A

a measure of the damage done to a person’s body by ionising radiation

72
Q

what does the radiation dose depend on? 3

A

the type of radiation used
how long the person is exposed to it
the energy the person absorbs from the radiation

73
Q

what is radiation dose measured in?

A

sieverts (Sv)

74
Q

how are x rays produced?

A

when fast moving electrons hit a target in an x ray tube

75
Q

what can high doses of radiation cause?

A

killing live cells

76
Q

what can low doses of radiation cause?

A

gene mutation and cancerous growths

77
Q

2 natural sources of ionising radiation

A

cosmic radiation from space

radon gas from underground

78
Q

how many millisieverts are in a sievert?

A

1000

79
Q

how are xrays used to destroy tumours?

A

thick plates between x ray tube and body stops rays from damaging healthy cells
gaps in the plates allow rays to reach and destroy tumour

80
Q

what is the wavelength of an xray used for imaging like compared to one used for destroying cancerous tumours?

A

x rays used for imaging have wavelengths that are much longer

81
Q

why are longer wavelength xrays used for imaging

A

they don’t carry as much energy

82
Q

process of x ray imaging

A

x rays are directed at the body
they pass through soft tissues but are absorbed by denser materials
bones appear white because this is where less x rays pass through
a CCD converts x rays to light and produces an image

83
Q

what is a CCD and what does it do?

A

a Charge Coupled Device
sensors in the CCD convert x rays to light
light rays create electronic signals which are sent to a computer to create a visible image

84
Q

use of lead plates in x rays and why

A

placed between the tube and the patient to stop rays reaching other body parts
lead is a good absorber of x rays

85
Q

process of viewing internal organs

A

patient is given a barium meal
barium absorbs x rays like bones
this shows where blockages are on a radiograph

86
Q

what is a contrast medium?

A

a material that absorbs x rays easily

87
Q

what does the frequency of a wave determine?

A

the higher the frequency, the more energy transferred

88
Q

consequences of too much UV radiation? 4

A

sunburn
premature skin ageing
blindness
increased risk of skin cancer

89
Q

what is radiation dose?

A

a measure of the risk of harm from the body being exposed to radiation

90
Q

what happens when an object that is hotter than its surroundings cools down?

A

it emits more infrared radiation than it absorbs

91
Q

what do objects that are at a constant temperature do?

A

emit IR radiation at the same rate they are absorbing it

92
Q

what is a perfect black body?

A

something that absorbs all radiation that hits it

93
Q

why does the temperature of the earth increase in the day?

A

more infrared radiation is absorbed and less is emitted

94
Q

why does the temperature of the earth decrease at night?

A

less radiation is being absorbed than emitted

95
Q

what happens to the wavelengths emitted when the temperature of an object increases?

A

the intensity increases so the peak wavelength decreases

96
Q

what are the oscillations like on a transverse wave?

A

they oscillate perpendicularly to the direction of energy transfer

97
Q

examples of transverse waves 2

A

electromagnetic waves

ripples/waves on water

98
Q

examples of longitudinal waves 2

A 
sound waves in air
shock waves (eg seismic waves
99
Q

what are the oscillations like on a longitudinal wave?

A

parallel to the direction of energy transfer

100
Q

how does a microphone work?

A

alternating currents produce oscillating EM waves
the frequency of the waves and current are equal
EM waves travel to transmitter
audio signal supplied to transmitter modulates carrier waves
alternating current causes transmitter aerial to emit radio waves carrying the audio signal
waves received by receiver aerial
oscillations cause receiver to oscillate at same frequency
receiver separates audio signal from carrier waves
audio signal supplied to speaker
sound waves similar to those in radio station are emitted

Physics⚡️ (16 decks)

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