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Physics GCSE > topic 3 - waves and the em spectrum > Flashcards

topic 3 - waves and the em spectrum Flashcards

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1
Q

7 groups of the EM spectrum

A 
radio
micro
infrared
visible light
ultra violet
x-rays
gamma rays
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2
Q

wavelength range radiowaves

A

1m - 10^-4m

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3
Q

wavelength range microwaves

A

10^-2m

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4
Q

wavelength range infrared

A

10^-5m

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5
Q

wavelength range visible light

A

10^-7m

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6
Q

wavelength range ultraviolet

A

10^-8m

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7
Q

wavelength range x-rays

A

10^-10m

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8
Q

wavelength range gamma rays

A

10^-15m

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9
Q

what colour has the longest wavelength

A

red

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10
Q

what colour has the shortest wavelength

A

violet

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11
Q

how are EM waves made with a.c

A

alternating currents are made up oscillating charges

as charges oscillate, they produce oscillating electric and magnetic fields (EM waves)

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12
Q

how do radiowaves in a transmitter induce a.c in a receiver (5)

A

1) a.c supplied to transmitter
2) electrons oscillate to produce EM waves
3) emitted radio waves transfer energy
4) at receiver, EM waves are absorbed, causing electrons in the receiver to oscillate
5) this produces a.c in the receiver

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13
Q

uses of radiowaves (2)

A

broadcasting

communications and satellite transmissions

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14
Q

how are radiowaves used in broadcasting (3)

A

long wave radiowaves can be received halway around the world from where they started as they bend around the Earth’s curved surface

short wave radiowaves can be received at long distances from the transmitter as they are reflected by the Earth’s atmosphere (used by bluetooth)

very short wavelengths are used for tv and fm transmissions but in order to get a signal, the receiver has be in direct sight

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15
Q

uses of microwaves (2)

A

cooking

communications and satellite transmissions

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16
Q

how are microwaves used in cooking

A

microwaves are absorbed by water molecules in the food
they can penetrate a few cm before being absorbed and transferring the energy they are carrying to the water molecules causing it to heat up
water molecules transfer energy to rest of food molecules by heating

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17
Q

how are radiowaves and microwaves used in communications and satellite transmissions

A

microwaves or high frequency radiowaves
they pass easily through the Earth’s watery atmosphere to a satellite receiver dish orbiting the eearth
that transmits the signal back to earth in a different direction where it is received by a satellite dish

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18
Q

what is infrared radiation used for (6)

A 
cooking
thermal imaging
short range communications
optical fibres
TV remote controls
security systems
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19
Q

how is infrared radiation used for cooking

A

absorbing IR radiation causes objects to get hotter so food can be cooked using IR radiation as the temperature of the food increases

20
Q

how is infrared radiation used for thermal imaging

A

infrared cameras can be used to detect infrared radiation and monitor temperature
camera detects IR radiation, converts it to an electrical signal and this is displayed on a screen as a picture
this is used by the police to see suspects trying to escape or hide in the dark

21
Q

how is infrared radiation used for short range communications

A

transfer of information across short distances
the receiver has to be in the line of sight of the emitter
can be used to send files between mobile phones or laptops

22
Q

how is infrared radiation used for optical fibres

A

thin glass or plastic fibres can carry data over long distances as pulses of IR radiation (usually uses one wavelength to prevent dispersion)
uses total internal reflection to send data over long distances

23
Q

how is infrared radiation used in tv remote controls

A

transfer data over a short distance from the remote to the TV
some phones have the software builtin to do this now

24
Q

how is infrared radiation used in security systems

A

if a change in infrared radiation is detected, an alarm sounds or a security light turns on

25
Q

what is visible light used for (3)

A

vision
photography
illumination

26
Q

how is visible light used for vision

A

visible light is the light we see

27
Q

how is visible light used for illumination

A

we use the light we see for lighting up things in order to be able to see them

28
Q

how is visible light used for photography

A

traditional photography uses photographic film which reacts to form an image
digital photography contains image sensors that detected visible light and generate an electrical signal which is converted to an image that can be stored digitally or printed

29
Q

what is UV light used for (4)

A

security marking
fluorescent lamps
disinfecting water
detecting forgery

30
Q

how is UV light used for security marking

A

security pens can mark property

under UV light the ink will glow but it is invisible otherwise , helping to identify stolen property

31
Q

how is UV light used for fluorescent lamps

A

fluorescent chemicals absorb UV radiation and then emit visible light
fluorescent lights use UV to emit visible light and are energy efficient

32
Q

how is UV light used for disinfecting water

A

used to sterilise water sometimes

it kills bacteria in the water making it safe to drink

33
Q

how is UV light used for detecting forgery

A

genuine bank notes and passports have special markings that only show up under UV light

34
Q

what are X-rays used for (3)

A

internal structure observation
airport security scanners
medical x-rays

35
Q

how are x-rays used for internal structure observation

A

x-rays affect photographic film in the same way as light

so you can take x-way photographs to view internal structure

36
Q

how are x-rays used for airport security scanners

A

used to detect hidden objects that can’t be detected using metal detectors

37
Q

how are x-rays used for medical x-rays

A

radiographers take x-rays to help identify broken bones
x-rays are transmitted by flesh by absorbed by denser materials
radiation is passed through the object or body onto a detector (the brighter parts are where fewer x-rays got though) producing a negative image

38
Q

what are gamma rays used for (3)

A

sterilisation of food/medical equipment
cancer detection
cancer treatment

39
Q

how are gamma rays used for sterilisation of food/medical equipment

A

works by gamma rays killing microbes
this keeps food fresh to eat for longer
sterilising medical equipment by killing microbes is good

40
Q

how are gamma rays used for cancer detection

A

can be detected using tracers which use gamma rays

41
Q

how are gamma rays used for cancer treatment

A

we can target cells with gamma radiation but doctors have to be careful not to cause damage to healthy cells nearby

42
Q

dangers of microwaves

A

some wavelengths of microwaves can be absorbed causing internal heating of cells which can be dangerous

43
Q

dangers of IR radiation

A

can cause burns if skin gets too hot

44
Q

dangers of UV light (3)

A

ionising radiation
damage to surface cells that could lead to skin cancer
damager to eyes causes eye conditions or blindness

45
Q

dangers of x-rays and gamma rays

A

can potentially cause mutations and damage to cells
potentially leading to cancer
due to higher frequencies, more energy is transferred so more damage

Physics GCSE (10 decks)

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