Chapter 13 Flashcards
(100 cards)
1
Q
why do different types of each wave have different effects?
A
the energy they transfer depends on the wavelength of the waves
2
Q
what are the 7 waves?
A
Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays
3
Q
wavelength of radio waves
A
between 1m and 1 x 10^4 metres
4
Q
what type of waves are electromagnetic waves?
A
transverse
5
Q
what do EM waves do?
A
transfer energy from a source to an absorber
6
Q
wavelength of microwaves
A
10^-2 metres
7
Q
wavelength of infrared
A
10^-5 metres
8
Q
wavelength of visible light
A
10^-7 metres
9
Q
wavelength of ultraviolet
A
10^-8 metres
10
Q
wavelength of x rays
A
10^-10 metres
11
Q
wavelength of gamma rays
A
10^-15 metres
12
Q
what happens to the wavelength as you go down the spectrum (from radio waves to gamma rays)
A
decreases
13
Q
what happens to the frequency as you go down the spectrum (from radio waves to gamma rays)?
A
increases
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
15
Q
how fast do all EM waves travel in a vacuum or in space?
A
3x10^8 metres/second
16
Q
equation for wavespeed
A
wavespeed (m/s) = frequency (Hz) x wavelength (m)
17
Q
what is white light?
A
light that comes from the sun and ordinary lamps
18
Q
which colour has the longest wavelength?
A
red
19
Q
which colour has the shortest wavelength?
A
violet
20
Q
what do all objects emit?
A
infrared radiation
21
Q
what happens to the amount of infrared radiation emitted as the object gets hotter?
A
it increases
22
Q
why is infrared radiation so damaging?
A
it heats up cells to can damage or kill them
23
Q
why is infrared used in optical fibres?
A
it is absorbed by the glass fibres less than visible light
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
25
why are microwaves used in ovens?
they penetrate food and are absorbed by the water molecules, transferring their energy and heating it
26
how are microwaves used in satellites?
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
27
why and how is infrared used in TV remote controls?
they are easily produced and received
| the controller sends out a series of infrared pulses
28
how do infrared cameras work?
they detect infrared radiation and convert it to an electrical signal, which is displayed on a screen
29
how do infrared heaters work?
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
30
uses of microwaves 2
communications (satellites)
| heating food
31
properties of microwaves 3
absorbed by water molecules
can travel long distances
usually not harmful
32
uses of infrared 3
remote controls
heating
thermal imaging
33
properties of infrared 2
easy and cheap to produce with not much power
| can be felt but not seen
34
uses of radio waves 3
mobile phones
radios
TVs
35
properties of radio waves
can travel long distances
low energy
normally not harmful
36
why can micro and radio waves be dangerous?
they can penetrate and heat the body
37
what are the four carrier waves?
radio waves
infrared
visible light
microwaves
38
what are carrier waves?
used to carry a signal
39
properties of shorter wavelength radio waves? 2
carry more information
| smaller range
40
what are fibre optics and how do they work?
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
41
benefits of fibre optic over radio/microwaves? 2
```
carry more information (shorter wavelength)
more secure (signal can't leave fibre)
```
42
why are microwaves commonly used with satellites? 2
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
why are radiowaves with short wavelengths used for TV broadcasting from masts?
they carry more information s
44
why can long wave radio wavelengths be transmitted and received around the world?
the long wavelengths diffract around the curved surface of the earth
45
why can short wave radio wavelengths be transmitted and received around the world?
they are reflected from the ionsphere so zigzag around the world to their destination
46
what is the ionsphere?
an electrically charged layer in the earth's upper atmosphere
47
how does Bluetooth work?
it uses short wave radio wavelengths to send data over short distances
48
what are electromagnetic waves made from?
oscillating electric and magnetic fields
49
what are alternating currents made from
oscillating charges
50
what is produced when alternating currents oscillate?
electric and magnetic fields (EM waves)
51
why do microwaves heat food faster than normal ovens?
the waves penetrate into the food and are directly absorbed by it
52
why don't ovens absorb microwaves?
they don't contain water molecules
53
uses of infrared radiation 3
remote control
night vision
heating
54
properties of infrared?
easy and cheap to produce, can be felt but not seen
55
uses of visible light 3
seeing
lighting
signalling
56
properties of visible light 2
different colours
| can reflect and refract
57
uses of ultraviolet 2
sun beds
| security marking
58
properties of ultraviolet 3
3 types: UVA/B/C
can be harmful in large doses
can be seen by insects
59
uses of x rays 2
seeing inside body
| luggage scanners
60
properties of x rays 3
can penetrate thin materials
blocked by dense materials like bones
harmful
61
uses of gamma rays 2
treat cancer cells
| kill bacteria
62
properties of gamma rays 2
highly penetrative
| very dangerous - can kill cells
63
what is fluorescence?
when certain chemicals absorb ultraviolet rays and emit visible light
64
why are ultraviolet waves harmful to human eyes?
they carry more energy than visible light
65
differences between x rays and gamma rays
x rays are produced when electrons moving at high speeds are stopped
gamma rays are produced by unstable nuclei releasing electrons
66
what is ionisation?
when x rays or gamma rays knock electrons out of an atom, making it charged
67
why is ionising radiation so dangerous?
it can ionise and damage healthy body cells
68
why are x and gamma rays used in radiotherapy?
they can kill living cells
69
why are gamma rays used as tracers?
the gamma rays pass out of the body and can be detected so the source is tracked
70
what is the wavelength of an x ray the same as?
the diameter of an atom
71
what is radiation dose?
a measure of the damage done to a person's body by ionising radiation
72
what does the radiation dose depend on? 3
the type of radiation used
how long the person is exposed to it
the energy the person absorbs from the radiation
73
what is radiation dose measured in?
sieverts (Sv)
74
how are x rays produced?
when fast moving electrons hit a target in an x ray tube
75
what can high doses of radiation cause?
killing live cells
76
what can low doses of radiation cause?
gene mutation and cancerous growths
77
2 natural sources of ionising radiation
cosmic radiation from space
| radon gas from underground
78
how many millisieverts are in a sievert?
1000
79
how are xrays used to destroy tumours?
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
what is the wavelength of an xray used for imaging like compared to one used for destroying cancerous tumours?
x rays used for imaging have wavelengths that are much longer
81
why are longer wavelength xrays used for imaging
they don't carry as much energy
82
process of x ray imaging
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
what is a CCD and what does it do?
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
use of lead plates in x rays and why
placed between the tube and the patient to stop rays reaching other body parts
lead is a good absorber of x rays
85
process of viewing internal organs
patient is given a barium meal
barium absorbs x rays like bones
this shows where blockages are on a radiograph
86
what is a contrast medium?
a material that absorbs x rays easily
87
what does the frequency of a wave determine?
the higher the frequency, the more energy transferred
88
consequences of too much UV radiation? 4
sunburn
premature skin ageing
blindness
increased risk of skin cancer
89
what is radiation dose?
a measure of the risk of harm from the body being exposed to radiation
90
what happens when an object that is hotter than its surroundings cools down?
it emits more infrared radiation than it absorbs
91
what do objects that are at a constant temperature do?
emit IR radiation at the same rate they are absorbing it
92
what is a perfect black body?
something that absorbs all radiation that hits it
93
why does the temperature of the earth increase in the day?
more infrared radiation is absorbed and less is emitted
94
why does the temperature of the earth decrease at night?
less radiation is being absorbed than emitted
95
what happens to the wavelengths emitted when the temperature of an object increases?
the intensity increases so the peak wavelength decreases
96
what are the oscillations like on a transverse wave?
they oscillate perpendicularly to the direction of energy transfer
97
examples of transverse waves 2
electromagnetic waves
| ripples/waves on water
98
examples of longitudinal waves 2
```
sound waves in air
shock waves (eg seismic waves
```
99
what are the oscillations like on a longitudinal wave?
parallel to the direction of energy transfer
100
how does a microphone work?
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
