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physics > Light and the EM Spectrum - topic 4 > Flashcards

Light and the EM Spectrum - topic 4 Flashcards

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1
Q

what happens when a light ray hits the surface

A

it reflects off the surface

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2
Q

what is the law of reflection

A

the angle of incidence = angle of reflection

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3
Q

what is refraction

A

the change in direction of a wave passing from one medium to another is caused by its change in speed

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4
Q

what happens if the light wave is going from a less dense medium to a more dense medium

A

propagation of light will slow down and will bend towards the normal

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5
Q

what are the 2 types of reflection

A

specular reflection and diffuse reflection

diffuse diffusion

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6
Q

what is specular reflection

A

when reflection is perfect due to reflection from the smooth surface

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7
Q

what is diffuse reflection

A

reflection is imperfect due to a rough surface

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8
Q

colours of visible light from longest to shortest

A

red
orange
yellow
green
blue
indigo
violet

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9
Q

why are all colours revealed when white light passes through a prism

A

all colours individually have different wavelengths and travel at different speeds so are refracted by different amounts

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10
Q

what happens when white light hits a coloured surface

A

white light is absorbed along with all of its colours aside from the colour of the object

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11
Q

what are the two types of lenses

A

convex

concave

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12
Q

what type of image does convex lens form

A

real image

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13
Q

what type of image does concave lens form

A

virtual image

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14
Q

what type of waves are EM waves

A

transverse waves

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15
Q

order of EM waves from longest to shortest

A

radiowaves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays

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16
Q

the higher in temp an object is……

A

the more infrared radiation it emits

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17
Q

amount of energy the object absorbs must be……

A

the same as the amount of energy the object radiates

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18
Q

what colour is the best emitter and absorber of infrared radiation

A

Matte Black

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19
Q

what colour is the best reflector of infrared radiation

A

white

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20
Q

harmful effects of microwaves

A

internal heating of body cells

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21
Q

harmful effects of infrared

A

skin burns

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22
Q

harmful effects of UV light

A

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

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23
Q

harmful effects of x-rays/ gamma rays

A

mutation/damage to cells in the body

24
Q

uses of radio waves

A

broadcasting, communications, satellite transmissions

25
Q

uses of microwaves

A

cooking, communication, satellite transmissions

26
Q

conditions for total internal refraction

A

light ray has to go from more to less dense medium

the angle of incidence has to be greater than the critical angle

27
Q

uses of infrared

A

cooking, thermal imaging, short-range communication, tv remote controls

28
Q

uses of visible light

A

vision, photography

29
Q

uses of UV

A

security markings, disinfecting water, detecting forged banknotes

30
Q

uses of x-rays

A

airport security scanners, medical x-rays

31
Q

uses of gamma rays

A

sterilising food and medical equipment and detecting cancer and its treatment

32
Q

what is total internal reflection

A

where the ray is reflected back into the first material instead of being transmitted into the new material

33
Q

what are the two types of lenses

A

converging and convex

34
Q

what is focal length

A

the distance from the centre of a lens to its principal focus

35
Q

what type of images do converging lens form

A

real images

36
Q

what type of images are formed by diverging lens

A

Upright, diminished and virtual images

37
Q

when is a real image formed

A

when the light rays from a point on an object come together to form an image

38
Q

when are virtual images formed

A

when light rays don’t actually come together to form an image

39
Q

what do you need to say when describing an image

A

how big it is compared to the object
whether it is upright or inverted
whether it is real or virtual

40
Q

how does the focal length and shape of a lens affect its power

A

the shorter the focal length and the more curved the lens is, the more powerful the lens

41
Q

differences between converging and diverging lenses

A

converging lenses can produce real or virtual images and diverging can only produce virtual images

converging lens converge light, diverging lens diverge lens

42
Q

what speed do EM waves travel at in a vacuum

A

at the same speed

43
Q

what happens if the average power emitted by an object is larger than the average power absorbed by the object

A

the object will cool down

44
Q

what happens if the average power emitted by an object is smaller than the average power absorbed by the object

A

the object heats up

45
Q

what colour is the best absorber and emitter of radiation

A

black

46
Q

what type of surface is the best absorber and emitter of radiation

A

matt

47
Q

when does total internal reflection occur

A

when a wave is travelling into a less dense material
AND when the angle of incidence is larger than the critical angle

48
Q

what types of wave is a sound wave

A

longitudinal

49
Q

what type of wave is a light wave

A

transverse

50
Q

what speed do all EM waves travel at in a vacuum

A

3x10^8 m/s

51
Q

what happens if an atom absorbs energy

A

some of its electrons move to higher energy levels

52
Q

what happens when each electron falls back down to a lower level

A

an em wave is produced

53
Q

when are gamma rays produced

A

when there’s a change in the nuclei of atoms

54
Q

when are gamma rays emitted

A

when the nucleus needs to get rid of extra energy

55
Q

how are radio waves produced

A

using an alternate current in an electrical circuit .
As charges oscillate they produce oscillating electric and magnet fields.

56
Q

what does intensity and wavelength distribution depend on

A

their temperature

physics (14 decks)

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