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PHYSICS IGCSE > Light waves, em. spectrum and lens > Flashcards

Light waves, em. spectrum and lens Flashcards

1
Q

Name 4 properties of images in plane mirrors.

A
  • upright
  • virtual (real light rays do not come together)
  • laterally inverted
  • same size as object
  • image is same perpendicular distance behind the mirror as the object is in front
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2
Q

Is an image in a plane mirror real or virtual?

A

virtual (real light rays do not come together)

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3
Q

What happens to light as it enters a different medium?

A

changes speed and direction

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4
Q

When light goes from a LESS dense to a MORE dense medium, what happens to the refraction?

A

refraction is towards the normal
i>r

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5
Q

When light goes from a MORE dense to a LESS dense medium, what happens to the refraction?

A

refraction is away from the normal
i<r

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6
Q

What happens in refraction when the angle of incidence is 0?

A

no refraction

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7
Q

What is the critical angle?

A

angle between incident ray and normal, when the refracted ray is parallel to mediums surface

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8
Q

What is refractive index (n)?

A

the ratio of the speeds of a wave in two different regions

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9
Q

What causes total internal reflection?

A

when angle of incidence is greater than the critical angle
when wave speeds up after crossing boundary

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10
Q

How does an optic fibre work in telecommunication?

A

used to transmit optical pulses over long distances
short pulse of light produced at one end, travels along fibre, totally internally reflecting

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11
Q

What are properties of an image formed when object is beyond 2F?

A

real
upside down (inverted)
diminished

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12
Q

What are properties of an image formed when object is in between F and 2F?

A

real
upside down (inverted)
magnified

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13
Q

What are properties of an image formed when object is in between F and the lens?

A

virtual
upright
magnified

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14
Q

Formula for magnification

A

img height/object height or /img distance/object distance

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15
Q

How is a virtual image formed?

A

when diverging rays are extrapolated (extended) backwards, not forming a visible screen projection

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16
Q

How can short-sightedness be corrected?

A

adding a diverging lens in front of the cornea

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17
Q

How can long-sightedness be corrected?

A

adding a converging lens in front of the cornea

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18
Q

What is the focal length?

A

distance along principal axis from centre of lens to principal focus

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19
Q

What is the focal point/principal focus?

A

light parallel to principal axis incident on the lens is refracted and meet at the focal point

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20
Q

What is the principal axis?

A

the line that passes through both the centre of the lens surfaces and their centres of curvature

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21
Q

What is monochromatic?

A

visible light of a single frequency

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22
Q

order of rainbow (visible spectrum)

A

ROY G BIV

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23
Q

Which colour is refracted the least? Which one the most?

A

red the least
violet the most

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24
Q

What is the speed of red light compared to the others? How does this affect refraction?

A

faster
refracts less

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25
Q

What is the speed of violet light compared to the others? How does this affect refraction?

A

slower
refracts more

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26
Q

In glass, what are the relative wavelengths of red and violet light?

A

wavelength of red is bigger than wavelength of violet

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27
Q

State properties of red light.

A
  • faster
  • refracts less
  • greater wavelength
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28
Q

State properties of violet light.

A
  • slower
  • refracts more
  • smaller wavelength
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29
Q

State the main regions of the electromagnetic spectrum in order of wavelength, from longer to shorter.

A

radio waves
micro waves
infrared
visible light
ultra violet
x rays
gamma rays

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30
Q

State the main regions of the electromagnetic spectrum in order of frequency, from low to high.

A

radio waves
micro waves
infrared
visible light
ultra violet
x rays
gamma rays

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31
Q

How is the wavelength and the frequency in radio waves?

A

large wavelength
low frequency

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32
Q

How is the wavelength and the frequency in gamma rays?

A

short wavelength
high frequency

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33
Q

All electromagnetic waves travel at the ______ speed in a vacuum.

34
Q

State typical uses of radio waves.

A

radio and television transmissions
astronomy
radio frequency identification

35
Q

State typical uses of microwaves.

A

satellite television
mobile phones
microwave ovens

36
Q

State typical uses of infrared.

A

electric grills
short range communications (eg TV control remotes)
intruder alarms
thermal imaging
optical fibres

37
Q

State typical uses of visible light.

A

vision
photography
illumination

38
Q

State typical uses of ultraviolet.

A

security marking
detecting fake bank notes
sterilising water

39
Q

State typical uses of X-rays.

A

medical scanning
security scanners

40
Q

State typical uses of gamma rays.

A

sterilising food
sterilising medical equipment
detecting and treating cancer

41
Q

State typical uses of gamma rays.

A

sterilising food
sterilising medical equipment
detecting and treating cancer

42
Q

What are harmful effects on people of excessive exposure to microwaves?

A

internal heating of body cells

43
Q

What are harmful effects on people of excessive exposure to infrared?

A

skin burns

44
Q

What are harmful effects on people of excessive exposure to ultraviolet?

A

damage to surface cells and eyes, leading to skin cancer/eye conditions

45
Q

What are harmful effects on people of excessive exposure to X-rays and gamma rays?

A

mutation or damage to cells in the body

46
Q

What is the speed of electromagnetic waves in a vacuum?

A

3 x 10ˆ8 m/s

47
Q

What is the speed of electromagnetic waves in air?

A

approximately same as vacuum

48
Q

What type of electromagnetic radiation is used for communication with artificial satellites?

A

microwaves

49
Q

What do satellite phones use?

A

some use low orbit artificial satellites
some use geostationary satellites

50
Q

What does direct broadcast satellite television use?

A

geostationary satellites

51
Q

What are geostationary satellites used for?

A

some satellite phones
direct broadcast satellite television

52
Q

What are low orbit artificial satellites used for?

A

some satellite phones

53
Q

What do mobile phones and wireless internet use?

A

microwaves

54
Q

Why are microwaves used for mobile phones and wireless internet?

A

microwaves can penetrate some walls
only require a short aerial (antenna) for transmission and reception

55
Q

What does bluetooth use?

A

radio waves

56
Q

Why are radio waves used for bluetooth?

A

radio waves pass through walls (but signal is weakened if this happens)

57
Q

What are uses of optical fibres?

A

cable television
high-speed broadband

58
Q

Why is glass used in optical fibres?

A

it is transparent to both visible and some infrared light

59
Q

What two waves can carry high rates of data (optical fibre)?

A

visible light
some infrared

60
Q

What is an analogue signal?

A

signal can be any level within a range and varies continuously

61
Q

What is a digital signal?

A

signal has fixed values, information is sent in pulses of fixed duration (eg binary)

62
Q

What are benefits of digital signaling?

A
  • increased rate of transmission of data
  • increased range
63
Q

Why does digital signalling increase range?

A

because of accurate signal regeneration

64
Q

what is angle of incidence?

A

angle between normal and ray of light

65
Q

what is angle of reflection?

A

angle between reflected ray and normal

66
Q

what is refraction

A

when waves change speed and direction when passing from one medium to another

67
Q

when light travels from a less dense medium to another what happens

A

it bends towards the normal

68
Q

lens can be

A

diverging or converging

69
Q

diverging lens (mari ignora)

A

espalha dps de passar

70
Q

converging lens (mari ignora)

A

junta dps de passar

71
Q

when top of an image is formed below the optical axis, the image is

72
Q

when image is formed by extension of light rays, the image is

73
Q

what is principal focus

A

point where rays of light travelling parallel to axis meet and converge

74
Q

what is focal length

A

distance between centre os lens and focal point

75
Q

how is long sight corrected

A

converging lens

76
Q

how is short sight corrected

A

diverging lens

77
Q

what is dispersion

A

splitting of white light through a glass prism into each colour

78
Q

order of colours from longest to shortest wavelength

A

red
orange
yellow
green
blue
indigo
violet

79
Q

order of colours from shortest to longest frequence

A

red
orange
yellow
green
blue
indigo
violet

80
Q

what do analogue signals have

A

continuous electrical signals

81
Q

what do digital signals have

A

non-continuous electrical signals

82
Q

is sound transmitted as analogue or digital

PHYSICS IGCSE (20 decks)

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