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Physics > em waves types > Flashcards

em waves types Flashcards

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1
Q

What are all em waves

A

Transverse

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2
Q

where do all em waves travel the same speed in

A

a vacuum

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3
Q

what speed do they travel in it

A

3x10 to the power of 8

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4
Q

how do they transfer energy

A

from a source to an absorber

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5
Q

give an example

A

ir radiation emitted from hot object absorbed by surrounding air

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6
Q

what is the em wave spectrum ordered in

A

the increasing frequency and decreasing wavelength or increasing wavelength and decreasing frequency

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7
Q

what is the part of the spectrum humans can see

A

visible light

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8
Q

what is an alternating current made of

A

oscillating charges

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9
Q

what does the frequency of the ac current determine

A

the frequency of wave we produce

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10
Q

what device transmits and recieves the ac

A

transmitter and reciever

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11
Q

what can we transfer using radio waves

A

nearly all types of information

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12
Q

what are very short radio waves used for

A

fm radio or tv

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13
Q
A
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14
Q

why do you get faulty radio signal when in the car

A

hills and surrounding other objects interfere with the direct
transmission path of the wave

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15
Q

what uses medium radio waves used to send data

A

bluetooth

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16
Q

what do oscilloscopes display

A

wave frequency of an alternating current

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17
Q

what are 2 types of microwaves

A

ones absorbed by water molecules and ones not absorbed by water molecules

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18
Q

what and how are the non water microwaves used for

A

communication using satelites. they pass through atmosphere which has a lot of water

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19
Q

how are they used

A

recieved by satelite and transmitted back down to earth detected by satelite dish to get satelite tv

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20
Q

how are water microwaves spread through food

A

conduction and convection

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21
Q

what is ir radiation used for

A

ir cameras /cooking in oven and grills without penetrating surface of food/electric heaters

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22
Q

how are oven and grills using ir radiation

A

metal is heated with ir and emits ir radiation

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23
Q

how are live organisms detected by ir cameras

A

they are hotter then surroundings so emit more ir radiation and appear brighter on ir camera

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24
Q

what allows visible light to be used for communication

A

optical fibres that transmit data fast over long distances without absorbing and or scattering light(specular)

25
Q

why are optical fibres used over copper wires

A

they can transmit much more data and there is less chance for it to be distorted in transmission

26
Q

what uses uv light that is human generated

A

sun beds

27
Q

what are x rays used for

A

viewing internal structure of the body

28
Q

what do staff operating x rays wear

A

lead aprons

29
Q

why are gamma rays used

A

to sterilise medical equipment and food and in medical tracers

30
Q

why are they used over boiling water

A

as they kill microorganisms without melting equipment or altering food

31
Q

what is the trade off

A

they can diagnose and treat disease but also ionise cells

32
Q

what is convex

A

a lense that bulges ouwards

33
Q

What is the focal point/principal focus

A

The point that rays of light converge

34
Q

how does a lens form an image and how does it help us to see an image better

A

they help us to see an image as sharper or larger(magnifying glass/microscope)
it forms an image by refracting light

35
Q

what are real images always

A

inverted

36
Q

virtual image are made from

A

2 imaginary lines

37
Q

what rays do concave lenses produce

A

virtual images

38
Q

what are virtual images

A

always upright

39
Q

concave lenses always produce

A

upright virtual images and the further they are from the lens the larger they are

40
Q

do virtual images form projections on screens

A

no

41
Q

what images can come from concave lenses vs convex lenses

A

concave - virtual
convex-virtual and real

42
Q

roygbiv

A

red orange yellow green blue indigo violet

43
Q

what has longest wavelength and highest

A

red has longest and violet has the shortest so the highest freq/energy

44
Q

what is specular reflection

A

reflection from a smooth surface in a single direction(eg mirror

45
Q

what is diffuse reflection

A

reflection from a rough surface that causes scattering(eg matte/why reflection cant be seen off a table)

46
Q

what is white light

A

a mixture of all colours in the soectrum

47
Q

the more freq/energy the more

A

the light is refracted

48
Q

How do colour filters work

A

They absorb certain wavelengths(colours) and transmit others

49
Q

The colour transmitted is

A

The colour of the filter

50
Q

Colour of an opaque object depends on

A

The wavelengths of light that are reflected the strongest

51
Q

wavelengths that are not reflected

A

are absorbed

52
Q

white light on a green surface will have

A

green reflected into our eyes

53
Q

object appears white

A

when all wavelengths re absorbed equally

54
Q

appears transparent when all light is transmitted an only some is reflected or absorbed

A

all light is transmitted an only some is reflected or absorbed

55
Q

body is in equilibrium when

A

it absorbs radiation at the same rate it emits radiation

56
Q

object appears black when all wavelengths are absorbed

A

when all wavelengths are absorbed

57
Q

Temperature can be regulated by

A

controlling how much incoming radiation is absorbed or emitted

58
Q

rescue teams use light coloured shiny emergency blankets

A

as they emit less radiation than dark matt surfaces keeping patient warm as less ir is emitted

59
Q
A

Physics (5 decks)

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