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Physics > SP5 Light And The Electromagnetic Spectrum > Flashcards

SP5 Light And The Electromagnetic Spectrum Flashcards

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1
Q

What is a ray diagram

A

It’s a way of modelling what happens when light is reflected or refracted

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2
Q

What’s a normal

A

A line drawn at right angles to the barrier/mirror

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3
Q

What are the incident angles

A

The incident angle is the angle between the normal and incident Ray - reflected Ray’s are always measured from the normal too

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4
Q

What’s the law of reflection

A

When waves are reflected, the angle of reflection is always equal to the angle of incidence

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5
Q

What’s refraction

A

When a wave changes direction due to entering a different material -

when light meets the interface along the normal/ at right angles there is no change in direction

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6
Q

How does light refract

A

It bends towards normal of it goes into a medium when is travels more slowly

Bends away from normal it it goes into normal where is travels faster

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7
Q

When the incidence angle increases the refraction angle…

A

Increased until the light passes along the interface

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8
Q

What’s total internal reflection

A

When the angle of incidence increases so much light is reflected inside glass -

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9
Q

What’s the critical angle

A

The angle of incidence when total internal refraction starts to happen

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10
Q

When does total internal reflection occur

A

At angles of incidence greater than the critical angle - light is totalling reflected by glass block

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11
Q

What happens when the critical angle is equal to the incidence angle

A

The refracted light passes along the interest with some light being reflected

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12
Q

What is diffuse reflection

A

When a material has a rough surface, light is scattered in all directions

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13
Q

What’s specular reflection

A

On very smooth surfaces such as mirrors, light reflects evenly

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14
Q

What is white light

A

The light from the sun, it’s actually made up of different colours that our eyes see as white

It can be split up into the colours of the visible spectrum using a prism

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15
Q

Why would a red object look red

A

It would look red because it reflects red and absorbed all the other colour

A white object looks white Becuase it reflects all of the colours

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16
Q

What are filters

A

Pieces of transparent material that absorb some of the colours in white light, etc a blue filter transmits blue light and absorbs all other colours

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17
Q

What’s a lens

A

A piece of transparent material shaped to refract light in particular ways

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18
Q

What does the power of th lens show

A

How much it bend light that passes through , a more powerful lens is more curved and bends more light

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19
Q

What’s a converging lens

A

Is fatter in the middle than the edges, it makes parallel Ray’s of light converge to a focal point

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20
Q

What’s the focal length

A

The distance between the focal point and the centre of the lens

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21
Q

What’s a diverging lens

A

Is thinner in the middle that the edges

The focal point is the point from when the Rays seem to be coming after passing through the lens (it’s where the rays are originally parallel

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22
Q

What can a converging lens be used for

A

Focus Ray’s of light on to s screen. An image can be projected in to a screen in this way - we call this a REAL IMAGE

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23
Q

What’s a real image and how is it made

A

When an image can be projected onto a screen and can only be formed by light rays that come together

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24
Q

What’s a virtual image and how is it formed

A

An object close to a converging lens will form a virtual image

It can not be projected onto a screen and appears to be on the same side of the lens as the object - it’s upright and Magnified

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25
Q

What kind of image of image do diverging lens produce

A

Virtual images that’s are the same way up and diminished and closer to the lens than object

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26
Q

What are the frequencies of light that are eyes can detect also known as

A

Viable light - different frequencies cause us to see different colours

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27
Q

Tell me about colour frequencies

A

Red is a lower frequency

Blue is a higher frequency

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28
Q

What animals can detect electromagnetic waves with high frequencies than visible light

A

Birds

29
Q

What type of waves are em waves

A

Transverse

30
Q

What speed to em waves travel at in a Vacuum

A

3x10^8 m/s

31
Q

Tell me about infra red

A

All objects emit infrared radiation, hotter the object - the more emitted

32
Q

Who discovered infrared

A

William Herschel when he put dark coloured filters on telescope to observe sun safely and noticed that different colours made his telescope different temperatures

He used this idea to split sunlight from a prism and out a thermometer on each colour - also measured a temperature just beyond red of the spectrum (no visible light)

Blue was coldest

Red was hottest

33
Q

Tell me in order the seven colours in the visible spectrum

A

Red, orange, yellow, green, blue, indigo, violet

Or

ROY G BIV

34
Q

What em waves have frequencies lower than visible light

A

Microwaves and radio waves

35
Q

What em Ray’s have higher frequencies that visible light

A

X Ray’s and gamma rays

36
Q

In the em spectrum higher frequency waves have…

A

Shorter wave lengths

Lower frequencies have King wave length

37
Q

Tell me the order of the em spectrum

A 
Highest frequency
Gamma rays
X Ray's
Ultraviolet
Visible light
Infrared
Microwaves
Radio waves
Lowest frequency
38
Q

What are most telescopes like

A

Curved mirrors to focus the em radiation to a central sensor

39
Q

What used are there for visible light

A

Light bulbs - emit visible light

Cameras detect it and record images

40
Q

What are some used for infrared

A

Used for Tv remote controls

Information sent along optical fibres sent via infrared radiation

A grill or toaster transfers energy by IR to cook food

41
Q

What are the uses of microwaves

A

Used for satellite transmissions eg mobile phone signals

Microwave ovens

42
Q

What are some uses of radio waves

A

Used for transmitting radio broadcasts for tv programs

Controllers on the ground communicate with space craft using ratio waves

43
Q

How are radio waves produced

A

By oscillations in electrical circuits

A metal rod can be used as an aerial to records radio waves

radio waves absorbed by metal and caused oscillations in electrical circuits

44
Q

How do radio waves travel

A

In straight lines unless reflected or refracted - some frequencies of radio waves refracted by ionosphere (part of atmosphere)

If refracted at a suitable angle they can send them back to earth

45
Q

What’s the part of the em spectrum that can’t be refracted by earths atmosphere

A

Microwaves

46
Q

The higher the temperature the shorter the…

A

Wavelengths

47
Q

The intensity(amount) of radiation emitted by an object increases as

A

It’s temperature increases

48
Q

What is the power

A

The amount of energy transferred in a certain amount of times

49
Q

What is power measured in

A

Watts (W) 1w=1j/s

50
Q

What must a system do to stay at a constant temperature

A

Must absorb the same amount of power as it radiates

51
Q

How much radiation does the earth absorb from the sun that reaches it

A

About half (51%)

52
Q

What happens when sun rays are abseiled by earth

A

Re radiated as infrared radiation which can warm up the atmosphere

53
Q

For earth to stay the same, it must…

A

Radiate energy into space at the same average rate it’s abstained

54
Q

Name some greenhouse gasses

A

Methane

Carbon dioxide

55
Q

What do greenhouse gases do

A

Absorb some energy from sun so earth is at a higher temperature

56
Q

What is believed to be the cause of the greenhouse effect

A

Humans have upset the natural balance by emitting more greenhouse gases

57
Q

Instead of Suns Ray’s being radiated back to space what do greenhouse gasses do

A

They absorb the energy that’s more than actsully needed

58
Q

How could the temperature of earth decrease again

A

If greenhouse gases were removed from the atmosphere it would hold less energy

59
Q

Tell me some uses of ultra violet

A

It transfers more energy than visible light, the energy transferred can be used to disinfect water by killing microorganism in it

Some materials absorb and remit uv at visible light called fluorescence that can be used for security markings as only visible when uv light shone on them

60
Q

Tell me some uses of X-rays

A

Can pass through materials visible light can’t - like muscles and fat but bone absorbs some X-rays so can be used in medicine to take images inside body

Can be used to examine insides of metal objects and inspect luggage in airport security scanners

61
Q

Tell me some uses of gamma rays

A

Transfer a lot of energy and and kill cells so used to sterilise surgical instruments and food

Used to kil cancer cells in radiotherapy which targets cancerous cells

Can be used to detect cancer by a chemical being injected into blood that emits gamma rays and collect inside cancer cells and a scanner locates the cancer by finding source of gamma rays

Gamma rays can pass through all materials in body

62
Q

What’s is a danger of microwaves at certain frequencies

A

Certain frequencies of microwaves can hear water and could damage us by heating and killing cells as we are Mostly water

63
Q

Tell me a danger about mobile phones

A

They use different microwave frequencies and emit and receive them but have not been around long enough to conclude any damage

64
Q

How can infrared be a danger

A

Too much IR radiation can damage or destroy cells causing burns

65
Q

How can UV RAYS cause be a danger

A

Too much can damage our DNA and too much exposure can lead to skin cancer

You can suffer snow blindness from too much Uv reflected from snow

66
Q

How can we protect ourselves from Uv

A

Clothing, hats, sun cream with a high SPF, sunglasses

67
Q

Tell me a danger of gamma and X rays

A

Have higher frequencies so can transfer more energy and excessive exposure can cause mutation in DNA to kill cells or cause cancer

68
Q

How is electron magnetic radiation caused

A

By changes in electrons or the nuclei in atoms

Radiation can also cause chafed I atoms such as losing electrons to become ions

Physics (13 decks)

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