P13 - EM Spectrum & Waves Flashcards
1
Q
What are Carrier waves?
A
Waves used to carry any type of signal
2
Q
What is a charge-coupled device (CCD)?
A
An electronic device that creates an electronic signal from an optical image formed on the CCD’s array of pixels
3
Q
What is a contrast medium?
A
An X-ray absorbing substance used to fill a body organ so the organ can be seen on a radiograph
4
Q
What is the electromagnetic spectrum?
A
The continuous spectrum of electromagnetic waves
5
Q
What is ionisiation?
A
The process by which atoms become charged
6
Q
What are microwaves?
A
Electromagnetic waves between infrared radiation and radio waves in the electromagnetic spectrum
7
Q
What is an optical fibre?
A
Thin glass fibre used to transmit light signals
8
Q
What is a radiation dose?
A
Amount of ionising radiation that a person receives
9
Q
What is a radiowave?
A
Electromagnetic waves of wavelengths greater than
0.1 m
10
Q
What is Ultraviolet Radiations (UV)?
A
electromagnetic waves between visible light and X-rays in the electromagnetic spectrum
11
Q
What is wave speed?
A
The distance travelled per second by a wave crest or trough
12
Q
What is white light?
A
Light that includes all colours of the spectrum
13
Q
What is the structure of an electromagnetic wave?
A
- Electromagnetic waves are transverse waves that transfer energy.
- Vibrations are electric and magnetic fields forming the EM wave.
- Electric and magnetic fields oscillate 90° to wave direction and to each other.
14
Q
What are the properties of an electromagnetic wave?
A
• They are transverse waves.
• They can travel through a vacuum (they do not require a medium to travel through).
• They travel at the speed of light
• EM waves with a high frequency have high energy, while low frequency waves have low energy
• They form a continuous spectrum
15
Q
What is an electromagnetic wave?
A
Electrical and magnetic disturbances that transfer energy from one place to another
16
Q
What is the order of the EM spectrum (from long wavelength to short) (low frequency to high)
A
-Radio Waves = LOW
-Microwaves
-Infrared
-Visible Light
-Ultraviolet Light
-X-rays
-Gamma radiation = HIGH
17
Q
What is the speed of light in a vacuum?
A
3.0×10^8m/s
18
Q
What is the equation for the speed of a wave?
A
Wave speed = Frequency x wavelength
19
Q
If a shiny white can of water and a matt black can of water are both heated by an infrared lamp, which will heat quickest?
A
- Black beaker water temperature increases more than white beaker water.
- Matt, dark surfaces absorb more infrared radiation.
- Shiny, light surfaces absorb less infrared radiation.
20
Q
What emits more infrared radiation, a shiny white surface or a matt black surface?
A
- Matt black surfaces: good emitters of infrared radiation
- Dark matt surfaces: excellent emitters of infrared radiation
- White shiny surfaces: poor emitters of infrared radiation
21
Q
If a matt black can and a white shiny can where both filled with hot water, which volume of water would be hottest after 5 minutes?
A
- Shiny white can = hottest water
- Shiny white = poor infrared emitter
22
Q
What are the properties of a short wavelength carrier wave?
A
• More information carried
• More energy carried
• Shorter range (greater absorption by the atmosphere)
• The less they spread out
23
Q
What are the properties of a long wavelength carrier wave?
A
• Less information carried
• Less energy carried
• Greater range (less absorption by the atmosphere)
• The more they spread out
24
Q
What can Ultraviolet light be used for?
A
• Sun beds
• Fluorescent materials
• Security
• Sterilisation
25
How can Ultraviolet light be used with fluorescent materials?
- Fluorescent materials absorb UV light and re-emit it as visible light.
- Used in fluorescent paint.
- Applied in fluorescent light bulbs (highly energy-efficient).
26
How can UV light be used in security?
Some types of ink are invisible until UV light is shined on it. They absorb the UV light and re-emit it as visible light. This can be used to mark valuable objects or money
27
How can UV light be used in sterilisation?
UV light destroys microorganisms
28
What are the 3 types of ionising radiation?
• UV Light
• X-rays
• Gamma radiation
29
What are the dangers of UV light?
- Harmful to human eyes, can cause blindness
- Harmful to skin: premature aging, sunburn
- Can cause skin cancer as it is ionizing
30
How can you protect yourself from the dangers of UV light?
- Use skin creams to block UV waves when staying outdoors in summer.
- Avoid looking directly at the sun or other UV light sources.
- Limit tanning bed use to the recommended time and wear protective goggles.
31
How are X-rays produced?
X-rays are produced when electrons or other particles travelling at high speeds are stopped. X-ray tubes are used to produce X-rays
32
How are gamma rays produced?
Gamma rays are produced when unstable nuclei in radioactive substances decay and release energy in the form of EM waves
33
What are some similarities of X-rays and Gamma Rays?
• Very high frequency
• Very low wavelength
• High penetrating power
• Will be stopped by a thick lead plate
34
Describe the penetrating power of Gamma rays and X-rays
- Gamma rays and X-rays are highly penetrating due to short wavelengths.
- Short wavelengths mean they carry more energy than longer wavelength EM waves.
- Gamma rays have shorter wavelengths than X-rays.
- Gamma rays are more strongly penetrating than X-rays.
35
What does a white piece of clothing look like under a UV lamp?
It glows blue, this is because many cleaning detergents contain fluorescent dyes to make white clothes brighter.
36
What are the dangers of X-rays and Gamma radiation, and how do you protect against them?
- Highly penetrative ionising radiation
- May cause cell mutations leading to cancer
- Protect with thick lead shielding
37
Describe how ionising radiation works?
- High-frequency radiation (UV, X-ray, Gamma) causes ionization by knocking out electrons.
- Ionization can damage living cells, leading to gene mutations and cancer growth.
- Higher doses of radiation can kill cells directly.
38
What is a CT scanner?
- ACT scanner: circular machine patient sits inside
- X-ray moves around inside ring
- X-rays released at each position
- Forms image of patient
39
What are the advantages of a CT scanner?
• It can form a 3d image
* It can distinguish between soft tissue
40
What are the disadvantages of a CT Scan?
• They are very expensive
* A higher dose of ionising radiation is administered to the patient
41
How is an X-ray image produced?
- X-ray tube emits rays through patient's body parts.
- Soft tissues allow X-rays to pass through, bones absorb them.
- Film/detector records X-ray exposure, making absorbed areas darker.
- Bones appear lighter (radiopaque) against darker background.
- Resulting image is a negative representation.
42
What does a hole or cavity in a tooth show up as in an X-ray?
A dark area in the bright image of the tooth
43
What are 2 advantages of using an X-ray?
• They can accurately show if bones are broken or teeth contain cavities
• They can be used to destroy cancerous tumours
44
What are 2 disadvantage of using X-rays?
• They are a form of ionising radiation, in high doses they may cause cancer
• They cannot distinguish between soft tissue
45
Why can UV waves be used to image organs and unborn babies?
- Ultrasound waves used for imaging unborn babies and organs inside the body.
- Waves partially reflected at body organs due to density differences.
- Reflection detected by transducer to form images.
46
What precautions are taken when using X-rays?
• People are limited in the number of X-rays they can receive
• A thick lead plate prevents radiations reaching healthy tissue during radiotherapy
• Shielded walls containing lead are built around the room
• Workers wear a thick lead apron
• Film badges are used to monitor radiation exposure
47
Describe one use of ultrasound for medical treatment (not medical imaging)
destruction of kidney stones
48
What is a source of a radio wave?
Radio waves re created when an alternating current in an electrical circuit creates an electromagnetic wave
49
What is the effect on the human body of a radiowave?
It passes straight through the body without being absorbed
50
What is 1 use of a radio wave?
It can be used to carry signals (they act as a carrier wave), this is because they have a long wavelength and therefore can travel very far
51
What is the effect on the human body of a microwave?
Some wavelengths of microwave can be absorbed, causing heating of cells, which may be dangerous
52
What is the source of infrared radiation?
All objects give off infrared radiation, the hotter the object, the more infrared radiation given off
53
What is the effect of infrared radiation on the human body?
It is mostly reflected or absorbed by the skin, causing heating. It may cause burns if too much is absorbed
54
What is the effect of visible light on the human body?
It is mainly reflected or absorbed, it may cause some slight heating effects
55
What is the effect on the human body of UV radiation?
- UV radiation has high frequency, transferring more energy.
- Ionizing nature can knock electrons out of shells.
- Damages cells, potentially causing genetic mutations.
- Associated with increased risk of cancer.
56
What is the effect of x-rays on the human body?
UV radiation has a high frequency, so it transfers more energy, therefore causing more damage. It is ionising as it can knock electrons out of their shell. This damages cells which may cause genetic mutations and cancer.
57
What do waves not transfer?
Matter
58
What is the wavelength of visible light?
400nm to 700nm
59
What are the uses of infrared radiation?
• Optical Fibres
• Remote control handsets
• Infrared scanners and cameras
• Electric heaters and cookers
60
Why is Infrared radiation used in optical fibres?
Infrared radiation is absorbed less than visible light in the glass fibres, this means the information will not be lost
61
Why is infrared radiation used in remote control handsets?
- TV remote handsets use Infrared radiation to transmit signals.
- Pressing a button sends out a sequence of Infrared pulses.
- Infrared is chosen because it's easy to generate and detect electronically.
62
Why is infrared radiation used in scanners and cameras?
- Infrared scanners detect infrared radiation from hot spots on the body.
- Hot spots may indicate unhealthy tissue beneath.
- Infrared cameras can see people, animals, and hot objects in darkness.
63
Why is infrared radiation used in electric heaters and electric cookers?
- Infrared radiation heats objects rapidly.
- Electric heaters use infrared to warm rooms quickly.
- Halogen hobs on electric cookers emit intense infrared for faster cooking.
- They heat food faster than conventional hobs by emitting more infrared radiation.
64
What are the uses of microwaves?
• Communications
* Heating food
65
Why are microwaves used for communications?
- Microwaves used in communications for satellites and mobile phones.
- Pass through atmosphere to reach satellites.
- Do not spread out much, ideal for satellite communication.
- Transmitter sends signal to satellite receiver dish.
- Satellite retransmits signal to Earth via satellite dish.
66
Why is a microwave used to heat food?
- Microwaves heat food faster than regular ovens.
- Microwaves penetrate food and are absorbed by water molecules.
- Water molecules transfer heat to surrounding food.
67
Why does a microwave oven not become hot like the food that it is cooking?
Microwaves are absorbed by water molecules in the food. The oven itself does not contain any water molecules and therefore does not become hot
68
What are radio waves with a wavelength less than 1m used for?
Transferring signals between TV masts and a TV as they can carry much more energy than longer waves and do not need to travel as far
69
What are radio waves with a wave length greater than 100m used for?
National and international radio stations because they have a much longer range than short-wavelength radio waves
70
What is an alternating current?
a current that repeatedly reverses its direction
71
Explain how a radio wave transfers signals
- Oscillator provides carrier waves to transmitter as AC.
- Audio signal modulates carrier waves in transmitter.
- Modulated waves sent to transmitter aerial emit radio waves carrying audio.
- Receiver aerial absorbs radio waves, inducing AC and causing oscillations.
- Receiver oscillations match radio wave frequency.
- Receiver circuit separates audio signal from carrier waves.
- Audio signal sent to device for sound reproduction.
72
How does an optical fibre work?
- Optical fibers are thin glass fibers used for signal transmission.
- They carry signals using visible light or infrared radiation.
- Light rays inside the fiber are trapped due to total internal reflection.
- The light is reflected continuously until it reaches the fiber's end.
- Minimal scattering or absorption of light occurs within the fiber.
73
What are the advantages of optical fibre communication?
• Optical fibres carry much more information as the light has a much shorter wavelength than radio waves
• The optical fibres are more secure than radio waves as the signals always stay within the fibres
74
What are the uses of X-rays?
• Medical Imaging
• Radiotherapy
• Detection of internal cracks in metal objects
75
What are radiographs?
An imaging technique using radiation to produce images of internal human structures
76
Why are X-rays used to detect internal cracks in metal objects
- denser objects absorb more X-rays, vice verca.
- Differences in X-ray absorption detectable on opposite sides of metal.
- Used to identify cracks within metal objects.
77
What are the uses of gamma radiation?
• Radiotherapy
• Sterilisation
• Radioactive tracers
78
What is a film badge and what does it do?
- Device with photographic film
- Monitors wearer's radiation exposure
- Registers level of radiation exposure
79
How can gamma radiation be used in sterilisation?
- Gamma rays have extremely high energy.
- Exposure to gamma rays kills 99% of disease-carrying bacteria and pathogens in food.
- Gamma rays can sterilize and eliminate harmful bacteria on medical instruments.
80
How can gamma radiation be used in radioactive tracing?
A gamma emitting source is injected into the patient, and so its progress around the body is followed as the gamma rays exit the body and are detected outside
81
How can organs made from soft tissue be imaged using an X-ray?
- Organ filled with contrast medium
- Absorbs X-rays
- Enhances visibility of internal surfaces
- Enables clear radiograph interpretation
82
What is a flat-panel detector and what does it do?
- Flat panel detector: Small screen with a CCD.
- CCD sensors convert X-rays to light.
- Light creates electronic signals in sensors.
- Signals sent to computer for digital X-ray image display.
83
What does a radiation dose depend on?
• The type of radiation used
• How long the body is exposed to the radiation
• The energy per second absorbed by the body from the radiation
84
What is the unit for radiation dose?
Sieverts (Sv)
85
What is the difference between X-rays used in imaging and X-rays used in radiotherapy?
- Therapy X-rays have higher energy than imaging X-rays.
- Low-energy X-rays are good for imaging as they pass through soft tissue and cracks in bones.
- They're absorbed by bones and teeth.
- Low-energy X-rays can't treat cancer; high-energy X-rays are needed for that.
