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physics > light and the electromagnetic spectrum > Flashcards

light and the electromagnetic spectrum Flashcards

1
Q

what does the angle of incidence =

A

angle of reflection

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2
Q

what is the angle of incidence

A

the angle between the incoming wave and the normal

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3
Q

what is the angle of reflection

A

the angle between the reflected wave and the normal

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4
Q

what is the normal and how is it usually shown

A

shown through a dotted line

it’s a imaginary line that’s perpendicular to the surface at the point of incidence

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5
Q

what does total internal reflection depend on

A

critical angle

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6
Q

what is specular reflection

A

when waves are reflected in a single direction by a smooth surface, means you get a clear reflection

e.g. when light reflects by a mirror

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7
Q

what is diffuse reflection

A

when waves are reflected by a rough surface and the waves are reflected in all directions
e.g. paper

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8
Q

how to investigate refraction using a glass block

A

1) place a rectangular glass block on a piece of paper and trace around it. Use a ray box to shine a ray of light at the middle of one side of the block.

2) Trace the incident ray and the emergent ray on the other side of the block. Remove the block and, with a straight line, join up the incident ray and the emergent ray to show the path of the refracted ray through the block.

3) Draw the normal at the point where the light ray entered the block. Use a protractor to measure the angle between the incident ray and the normal (the angle of incidence, I) and the angle between the refracted ray and the normal (the angle of refraction, R).

4) Do the same for the point where the ray emerges from the block.

5) Repeat this three times, keeping the angle of incidence as the ray enters the block the same.

6) Calculate an average for each of the angles.

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9
Q

what do colour and transparency depend on

A

absorbed wavelengths

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10
Q

colour

A

differences in absorption, transmission, and reflection of different wavelengths by different materials

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11
Q

what is white light a mix of

A

all the the different colours of light, all different wavelengths

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12
Q

objects which reflect all of the wavelengths of the visible light equally

A

white

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13
Q

objects which absorb all wavelengths of visible light

A

black

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14
Q

objects which transmit light

A

transparent (see through)
translucent (partially see through)

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15
Q

objects which do not transmit light

A

opaque objects

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16
Q

colours with long wavelengths and low frequency

A

reds, oranges, yellows and partially green

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17
Q

colours with short wavelengths and high frequencies

A

purple, blue into greens

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18
Q

what are the 2 main types of lens

A

converging
diverging

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19
Q

what is a converging lens

A

lens which bulges outwards on the middle, causes parallel rays of light to be brought together
also know as convex lens

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20
Q

what is a diverging lens

A

a lens which caves inwards, causes parallel rays of light to spread out

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21
Q

what is the principle focus of
converging lens

A

where rays hitting the lens parallel to the axis all meet

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22
Q

what is the principle focus of a diverging lens

A

the point where rays hitting the lens parallel to the axis appear to come from

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23
Q

what is the focal length

A

the distance from the centre of the lens to the principle focus

24
Q

which lens is the power positive

A

converging lens

25
Q

which lens is the power negative

A

diverging lens

26
Q

what does the power of the lens increase with

A

curvature

27
Q

draw a ray diagram for an image through a diverging lens

A

1) Pick a point on the top of the object. Draw a ray going from the object to the lens parallel to the axis of the lens.

2) Draw another ray from the top of the object going right through the middle of the lens.

3) The incident ray that’s parallel to the axis is refracted so it appears to have come from the principal focus (F). Draw a ray from the principal focus. Make it dotted before it reaches the lens (as it’s virtual here).

4) The ray passing through the middle of the lens doesn’t bend,

5) Mark where this ray meets the virtual ray. That’s the top of the image.

6) Repeat the process for a point on the bottom of the object.
When the bottom of the object is on the axis, the bottom of the image is also on the axis.

28
Q

how to draw a ray diagram for an image through a converging lens

A

1) Pick a point on the top of the object. Draw a ray going from the object to the lens parallel to the axis of the lens.

2) Draw another ray from the top of the object going right through the middle of the lens.

3) The incident ray that’s parallel to the axis is refracted through the principal focus (F). Draw a refracted ray passing through F.

4) The ray passing through the middle of the lens doesn’t bend.

5) Mark where the rays meet. That’s the top of the image.

6) Repeat the process for a point on the bottom of the object. When the bottom of the object is on the axis, the bottom of the image is also on the axis.

29
Q

what type of wave are electromagnetic waves

A

transverse

30
Q

what speed to electromagnetic waves travel

A

all the same in a vacuum (space)
different speeds in different materials

31
Q

what is electromagnetic waves wavelength

A

from 10 -15m to more than 10 (4) m

32
Q

how do you group EM waves

A

by wavelength and frequency

33
Q

what are the 7 types of waves

A

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

34
Q

which waves have the longest wavelength and low frequency

A

radio
micro
infrared

(visible sits in the middle)

35
Q

which waves have the shortest wavelength and high frequency

A

gamma
x rays
ultra violet

(visible sits in the middle)

36
Q

radio waves properties

A

transmitted through the body without be absorbed

37
Q

microwaves properties

A

can be absorbed

causing heating of cells

38
Q

infrared and visible light properties

A

reflected and absorbed

burns skin if it gets too hot

39
Q

ultraviolet properties

A

a type of ionising radiation

also absorbed by the skin but at a higher frequency

causes damage to cells - skin cancer

damage to eyes (blindness)

40
Q

x-rays and gamma rays properties

A

ionising - can cause mutations and damage cells

higher frequencies

transfers energy

absorbed by deeper tissue

41
Q

what does every object absorb and emit

A

EM radiation

42
Q

what’s the best emitter out of black and white surfaces

A

black

43
Q

what does radiation effect and why

A

the earths temperature as it depends on the amount of radiation it reflects, absorbs and emits

44
Q

what can cause a change to the earths overall temperature

A

changes to the atmosphere

45
Q

what is radiation like during the day

A

lots of it, some is reflected most is absorbed increasing the temp

46
Q

what is radiation like during the night

A

radiation is emitted by the atmosphere, clouds and the earths surface decreasing the temp

47
Q

what are EM waves made up of

A

oscillating electric and magnetic fields

48
Q

what are radio waves made up of

A

oscillating charges

49
Q

how can you produce radio waves

A

using alternate current in an electrical circuit. the object charges electrons oscillate to create the radio waves called a transmitter

50
Q

what are radio waves used for

A

communication and broadcasting

e.g. bluetooth, TV and FM radio

51
Q

what are microwaves and radio waves used by

A

satellites
e.g. tv signals and satellite phones

52
Q

what are microwaves used for

A

can be used for satellites
heating food

53
Q

what is infrared radiation used for

A

increase or monitor temperature

e.g. infrared cameras
thermal imaging
infrared sensors, security systems
transfer information

54
Q

what is visible light used for

A

photography - digital cameras and photographic film
seeing in general

55
Q

what is ultraviolet used for

A

fluorescent lamps
security pens
sterilise water

56
Q

what are x-rays used for

A

seeing inside of things
e.g. hospital photos to check broken bones

airport security scanners

57
Q

what are gamma rays used for

A

sterilise medical instruments and food - kill microbes

cancer treatment, can treat but can cause more damage to healthy cells too

physics (7 decks)

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