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Science > Light and Electromagnetic spectrum > Flashcards

Light and Electromagnetic spectrum Flashcards

1
Q

What is a ray diagram used for?

A

A way of modelling what happens when light is reflected or refracted

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2
Q

What do the rays show in a ray diagram?

A

The direction the waves are travelling in

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3
Q

What is a normal?

A

Line drawn at right angles to the barrier or mirror

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4
Q

What is the incident ray and the reflected ray?

A
  • Incident ray is the ray going towards the mirror or barrier
  • Reflected ray is the ray that is reflected back
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5
Q

What is the law of reflection?

A

When the angle of reflection (measured from the normal) is equal to the angle of incidence (this then means that it has been reflected

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6
Q

What happens when a wave moves into a different material and what is this called?

A

It changes direction because they change speeds in different materials - called refraction

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7
Q

What is the interface?

A

Something that separates two different materials or matters - the boundary

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8
Q

What happens when light meets the interface at right angles?

A

It means it has moved along the normal and has no change in direction

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9
Q

Where does light travel faster, through air or through glass/water

A

Air

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10
Q

What happens when light passes through water or glass with small angles of incidence?

A

Most is refracted out but a small amount is reflected

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11
Q

What is the angle of refraction?

A

The angle measured from the normal to the refracted ray

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12
Q

What is the relationship between the angle of incidence and the angle of refraction?

A

As the angle of incidence increases so does the refraction angle

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13
Q

What happens after the angle of refraction has increased so much that it is now along the interface at a right angle to the normal and the angle of incidence increases and what is it called?

A

If the angle of incidence increases any further, then the incidence ray will only reflect not refract anymore - it is called total internal reflection

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14
Q

What is the critical angle?

A

The minimum angle at where total internal reflection occurs

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15
Q

How do you investigate refraction?

A
  • Use a ray box with a single slit
  • Place glass block on paper and draw outline
  • See where light goes after exiting the glass and draw crosses on rays
  • Take block away and join crosses and lines before and after it enters the block
  • Measure angles of incidence and refraction
  • Repeat experiments at different angles
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16
Q

What is diffuse reflection?

A

When a light ray is reflected on a rough surface so the light is scattered in all directions

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17
Q

What is specular reflection?

A

When light is reflected on a smooth surface so it reflects evenly

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18
Q

Give examples of a source of white light?

A

the sun or lightbulbs

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19
Q

What is white light made up of

A

A mixture of different colours and can be split up into colours using the visible spectrum using a prism

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20
Q

What happens when white light hits a coloured surface?

A

Some colours that make it up are reflected and some are absorbed

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21
Q

How does an object become a certain colour?

A

It absorbs the other colours and reflects the colour it is

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22
Q

What does a filter do?

A

They are pieces of transparent material that absorb some of the colours in white light (e.g blue filters transmit blue light but absorb all the other colours)

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23
Q

What is a lens?

A

A piece of transparent material shaped to refract light in a certain way

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24
Q

What does the power of a lens describe?

A

How much it bends light that passes through it - a more powerful lens is more curved and bends the light more

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25
Q

What is a converging lens?

A
  • Fatter in the middle than at the edges

- Makes parallel rays of light converge at the focal point

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26
Q

What is the focal length?

A

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

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27
Q

What is a diverging lens?

A

-Thinner in the middle than at the edges

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28
Q

What is the focal point?

A

The point from which the rays seem to be coming after passing through the lens

29
Q

What is a real image?

A

An image that can be projected onto a screen

30
Q

How can real images only be formed?

A

By light rays that come together

31
Q

What is inverted?

A

Upside down

32
Q

What forms a virtual image?

A

An object close to a converging lens

33
Q

Why is an image called virtual?

A

Because it cannot be projected onto a screen

34
Q

What will a diverging lens always produce?

A
  • Virtual images that are the same way up

- Much smaller and closer to the lens than the object

35
Q

What is the name of the frequencies of light that our eyes can detect?

A

Visible light

36
Q

What type of waves are all EM wave?

A

Transverse waves

37
Q

Where do all EM waves travel at the same speed?

A

In a vacuum

38
Q

What do all objects emit energy by?

A

Infrared radiation

39
Q

What is the order of EM radiation in order of ascending frequency?

A

Radio waves, microwaves, infrared, UV, X-rays and gamma rays

40
Q

What type of radiation has the longest wavelength?

A

Radio waves (red)

41
Q

What do most telescopes use to focus the EM radiation onto a central sensor?

A

Curved mirrors

42
Q

What can visible light be used for?

A

Light bulbs

43
Q

What can infrared radiation be used for?

A

Communication at short ranges like computers in the same root or a TV to a remote control unit

44
Q

What can microwaves be used for?

A

Communication and satellite transmissions, including mobile phone signals

45
Q

What are radio waves used for?

A

Transmitting radio broadcasts and TV programmes

46
Q

How are radio waves transmitted?

A
  • The radio waves are produced by oscillations in electrical circuits
  • Metal rod/wire can be used as an aerial to receive the radio waves
  • The radio waves are absorbed by the metal and cause oscillations in electric circuits connected to the aerial
47
Q

What are oscillations?

A

Variations in current and voltage

48
Q

What is refraction?

A

The bending of the path of a wave due to a change in velocity

49
Q

What layer in the atmosphere can cause the refraction of some frequencies of radio waves?

A

The ioniosphere

50
Q

Are microwaves refracted in the Earth’s atompshere?

A

No

51
Q

Can radio waves be refracted in the Earth’s atmosphere?

A

Yes

52
Q

When does the intensity of radiation emitted by an object increase?

A

As its temperature increases

53
Q

What is the correlation between temperature and wavelength?

A

The higher the temperature, the shorter the wavelength

54
Q

What is the power of energy?

A

The amount of energy transferred in a certain time

55
Q

How does a system stay at a constant temperature?

A

It must absorb the same amount of power as it radiates

56
Q

Describe the Earth’s energy balance

A
  • Earth’s surface absorbs about 1/2 of radiation that reaches it from the Sun
  • Re-radiates this energy as IR radiation, which can warm up the atmosphere
  • For the temp of the Earth to stay the same, it must radiate energy into space at the same average rate it is absorbed
57
Q

What is the greenhouse effect?

A

Gases in our atmosphere that naturally absorb some energy, keeping the Earth at a higher temperature than if there were no atmosphere

58
Q

What would happen if some greenhouse gases were removed from the atmosphere?

A

The atmosphere would be able to hold less energy and its temperature would decrease

59
Q

What can UV radiation be used for?

A

To disinfect water by killing microorganisms in it

60
Q

What is fluorescence?

A

Materials that absorb UV radiation and re-emit it as visible light

61
Q

What are fluorescent materials often used for?

A

Security markings, where the materials are only visible when UV light shines on them

62
Q

What are X-rays used for?

A

In medicine to make images of inside of the body, as they can pass through muscles and fat easily but bone absorbs some X-rays

63
Q

What are gamma rays used for?

A

To sterilise food and surgical instruments by killing potentially harmful microorganisms (as they transfer a lot of energy and can kills cells)

64
Q

How can gamma rays be used to detect cancer?

A
  • A chemcial that emits gamma rays is injected into the blood
  • The chemical is designed to collect inside cancer cells
  • A scanner outside the body then locates the cancer by finding the source of the gamma rays
  • Gamma rays can pass through all materials in the body
65
Q

Which type of frequency of waves are more potentially dangerous?

A

Higher frequency waves, as they transfer more energy

66
Q

How can too much exposure lead to skin cancer?

A

Sunlight contains high frequency UV radiation, which is transferred to our cells and can cause sunburn and damage DNA, causing a mutation (cancer)

67
Q

What can excessive exposure to X-rays or gamma rays cause?

A

Mutations in DNA that can kill cells or cause cancer

68
Q

What is EM radiation produced by?

A

Changes in the electrons or nuclei in atoms

69
Q

What can radiation cause?

A

Changes in atoms, such as causing atoms to lose electrons to become ions

Science (23 decks)

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