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Physics > Section 2 - Waves and The Electromagnetic Spectrum > Flashcards

Section 2 - Waves and The Electromagnetic Spectrum Flashcards

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1
Q

what do waves transfer?

A

energy and information in the direction they are travelling

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2
Q

What is the amplitude of a wave?

A

The displacment from the rest position to a crest or trough

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3
Q

What is the wavelength of a wave?

A

length of afull cycle of a wave ( crest to crest )

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4
Q

What is the frequency of a wave?

A

the number of complete cycles of wave passing a cartain point per second

Mesured in Hz

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5
Q

What is the period of a wave?

A

the number of seconds it takes for one full cycle

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6
Q

What way do transverse waves vibrate?

A

Sideways, the vibrations are at 90degrees to the direction of the wave travel

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7
Q

What are some examples of transverse waves?

A

All electro magnetic waves
S waves
ripples and waves in water

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8
Q

what way do longitudinal waves vibrate?

A

parralel vibrations to the direction of the wave travel
They extend and compress

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9
Q

What are some examples of longitudal waves?

A

sound waves
P waves

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10
Q

What 3 things can happen to waves at boundaries?

A

Absorbed
Transmitted
Reflected

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11
Q

Wave ABSORBED

A

the wave transfers energy to the materials energy stores

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12
Q

Wave TRANSMITTED

A

the wave carries on travellign throughthe new material. This often leads to refraction

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13
Q

Wave REFLECTED

A

the incoming ray is neither absorbed or transmitted but instead is sent back “away” from the second material

Echos

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14
Q

What is Ultrasound?

A

sound with frequncies higher than 20,000Hz.

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15
Q

What happens to Ultrasound waves at boundaries?

A

They get partially reflected at boundaries ( some of the wave is reflected off )

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16
Q

What are some usefull ways to use Ultrasound? Why?

A

Pre-natal scanning of foetus
Industrial imaging

this is because when ultrasound reaches a medium boundary it is partially reflected. This reflection can be processed into a scan.

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16
Q

what is Infrasound?

A

Sound with frequencies lower than 20hz

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17
Q

What are some examples of Infrasound?

A

Whales and ELephants use it so communicate, this can be picked up and used to track these animals
Infraosund (seismic waves ) is released before an earthquake so scientists can pedict when the earthquak is going to happen

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18
Q

What are the two examples of Seismic waves?

A

P waves and S waves

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19
Q

P waves

A

They are LONGITUDINAL
they travel through solids and liquids
They travle faster than S waves

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20
Q

S waves

A

TRANSVERSE
onyl travle through solids
they are slower than P waves

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21
Q

What is the total intertial reflection

A

at what angle all of the wave is reflected
- Only happens when going from dense -> less dense material.

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22
Q

transparent vs translucent

A

When going through a transparent matter, the light rays stay parralel to eachother. Whereas when going through a translucent matter, the waves are scattered ( this means you cant see a clear image

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23
Q

When from a fast object to a slow one…

A

Light refracts towards the normal

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24
Q

When from a slow object to a fast one…

A

light refracts away from the normal

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25
Q

what is white light?

A

a mixture of all the different colours of light

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26
Q

What do opaque object do?

A

they do not transmit light.
They absorb some wavelengths of light and reflect others

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27
Q

Why do opaque objects have color?

A

They absorb some wavelengths of light, and refect other wavelengths, the wavelenghts corresponging to the visible spectrum reflected are the color the object is.

28
Q

Transmit

A

to pass through

29
Q

What do white objects do?

A

Reflect all wavelengths of visible light equally

30
Q

What do black objects do?

A

absorb all wavelenths of visible light
- are a lack of visible light

31
Q

Transparent

A

See through

32
Q

translucent

A

partially see through

33
Q

What do transparent and translucent objects do?

A

Transmit light - they appear as the color they most strongly transmit

34
Q

Color filters

A

only let particular wavelenths through
- used to filter out different wavelengths of light, and therefore onyl let certain ones through
- if a color is not transmitted through the filter the object will appear black

35
Q

EM waves

A
  • spectrum grouped on wavelength and frequency
  • transverse
  • all travel at the same speed in a vacuum but travel at different speeds in different materials
  • Vary in wavelength
  • eyes can only see the visible light
  • transfer energy from a source to an absorber
  • Higher frequency = more energy
36
Q

What are the three sections of the EM spectrum with long wavelengths?

A

Radio waves
Micro waves
Infrared

37
Q

What are the three sections of the EM spectrum with short wavelengths?

A

Ultra violet
X rays
Gamma rays

38
Q

Radio wave - Heath implications

A

transmitted throught he body without being absorbed- safe

39
Q

Micro wave - Heath implications

A

Some wavelengths can be absorbed, causing heating of cells - may be dangerous

40
Q

Infrared and Visible light - Heath implications

A

Mostly reflected or absorbed by skin, causing some heating. IR can burn

41
Q

Ultra Violet- Heath implications

A

Absorbed by skin but because it is a higher frequency is more dangerous.
- ionising radiation - when absorbed an cause damage to cells on the surface of skin -> can lead to cancer
- can damage your eyes - eye conditions and blindness

42
Q

X rays and Gamma rays- Heath implications

A
  • Ionising radiation - can cause mutations and damages to cells -> cancer
  • High frequency - high damage
  • can pass through skin and be absorbed by deeper tissues
43
Q

What is the order of the EM spectrum

A

Radio waves
Micro waves
Infrared
Visible light
Ultra Violet
X rays
Gamma rays

44
Q

Power

A

energy transferred per second

mesured in W

45
Q

Intensity

A

Power per unit area

46
Q

Visible light - uses

A

Light bulbs are designed to emit it
Cameras detect it and use it to capture images

47
Q

Infrared - uses

A
  • Communication at short distances
  • Optical fibres
  • Grills or toasters uses them to heat things up
  • thermal imaging -> Security systems
48
Q

Microwaves - uses

A
  • Communications ( mobile phone signals )and sattelite transmittions
  • Microwave oven - heating food
49
Q

Radiowaves - uses

A
  • transmitting radio broadcasts ( sattelites)
  • ground -> spacecraft
50
Q

how are Radiowaves produced

A

Produced by oscillating currents in electrical circuits - also can cause these

51
Q

Oscillate

A

go back and forwards

52
Q

Oscillating currents

A

Electrons moving backwards and forwards

53
Q

What path do waves travel in?

A

Straight lines unless reflected or refracted

54
Q

Refraction

A

the bending of a path due to a change in velocity

55
Q

The Ionosphere

A

The top part of the atmosphere
Some radiowaves and all microwaves pass through it
- if radiowaves reach the ionosphere at a suitible angle, they can be refracted back, allowing further travel.

56
Q

radiation and temperature

A

The intensity of radiation emitted by an object increases as it temperatures increases, the wavelengths also change with temp - Higher temp = more energy = shorter wavelength

57
Q

Radiate

emit

A

energy coming out of stuff

58
Q

absorb

A

energy coming into stuff

59
Q

Cold

A

absence of heat energy
colder things will absorb more heat

60
Q

How can something stay at a constant temperature?

A

It must absorb the same amount of heat energy it radiates
- Heat will spread from high temp to low temp untill a thermal equilibrium is reached

61
Q

The earths energy balance

A
  • absorbs about 1/2 the radiation t recves from the sun
    • radiates it as infrared
62
Q

The greenhouse effect

A

Some gases in our atmosphere ( mainly CO2 ) naturally abosrb some energy, keeping the earth at a higher temperature than if there were no atmosphere

63
Q

Specular

A

Waves are reflected in a single direction by a smooth surface - clear reflection

64
Q

Diffuse

A

Waves reflected by a rough surface are reflected in all directions - matt, no reflection

65
Q

Ultra-violet uses

A

Flourescent lamps
Sterilise water - kills bacteria

66
Q

X-rays uses

A

for x-ray images in hospitals or airport security scanners

67
Q

Gamma rays uses

A

Sterilise medical instruments - kill microbes
Cancer scanning or treatments

Physics (7 decks)

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