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Physics Gcse > ⭐️Topic SP5 - light and the EM spectrum > Flashcards

⭐️Topic SP5 - light and the EM spectrum Flashcards

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1
Q

How can you model wether light is reflected or refracted?

A
  • a ray diagram

- using waves on water

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2
Q

What is the normal?

A

The line on a ray diagram at right angles to the barrier/mirror

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3
Q

From where do you measure the angles of the incident ray and reflected ray?

A

From the normal

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4
Q

What is the law of reflection?

A

Where the angle of reflection is equal to the angle of incidence when waves are reflected

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5
Q

What is refraction?

A

Where light changes speed upon moving into a different material

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6
Q

When doesn’t light change direction when meeting a different density?

A

When it enters the material along the normal at right angles to the boundary

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7
Q

What happens to the reflection of light when it travels from water/glass to air with small angles of incidence?

A

Most of the light passes through the interface and little is reflected

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8
Q

What is total internal reflection?

A

When the angle of incidence is greater than the critical angle and the light is completely reflected inside the block

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9
Q

When does refracted light pass along the interface of the glass block?

A

When angle of incidence = angle of refraction.

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10
Q

What are non luminous objects?

A

Objects that do not reflect light

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11
Q

What is diffuse reflection?

A

Reflection from objects with a rough surface that cause the light to scatter in all directions.

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12
Q

Give an example of specular reflection

A

A mirror as light reflects evenly

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13
Q

What colours make up white light?

A

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

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14
Q

What does a prism do to light?

A

Split it up into a visible spectrum

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15
Q

Why does an object look a specific colour?

A

Because it absorbs all the colours of the spectrum but reflects the colour it looks

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16
Q

Why do object look white?

A

As it absorbs all colours

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17
Q

How can light be made coloured?

A

By transmitting the colour they look and absorbing the rest?

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18
Q

What colours in white light are transmitted and absorbed by red glass?

A

Red light is transmitted and all the other colours are absorbed

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19
Q

What does the power of a lens describe?

A

How much it bends light that passes through it

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20
Q

The more powerful a lens…

A

The more curved it is and the more it bends light

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21
Q

Describe a converging lens

A

It’s fatter in the middle than at the edges and makes parallel rays of light converge at the focal point

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22
Q

What is the focal length?

A

Distance between the focal point and the centre of the lens

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23
Q

Describe a diverging lens?

A

It’s thinner in the middle than at the edges and the rays seem to be coming from the focal point after passing through the lens

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24
Q

What is a real image?

A

An image that can be projected on a screen

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25
Q

What is needed to form a real image?

A

A converging lens as it can only be formed by rays that come together

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26
Q

What kind of image do you get you put an object near a converging lens?

A

A virtual image that looks bigger than the actual object and appears in front of the object

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27
Q

What kind of image do you get when you put an object far from a converging lens?

A

A real image that appears behind the lens, smaller than the object as upside down

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28
Q

What is a virtual image?

A

An image that can’t be projected onto a screen

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29
Q

What kind of image do diverging lenses always produce?

A

Virtual images that are the same way up and much smaller and closer to the lens that the object

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30
Q

What are the frequencies are eyes can detect referred to as?

A

Visible light

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31
Q

What kind of wave is light?

A

An electromagnetic wave?

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32
Q

What kind of waves are all em waves?

A

Transverse (their vibrations are at right angles in which the energy is being transferred by the wave)

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33
Q

What’s significant about the speed of em waves?

A

They all travel at the same speed of 3x10^8 m/s in a vacuum

34
Q

What do em waves do?

A

Transfer energy from the source to the observer

35
Q

What causes us to see different colours?

A

Different frequencies

36
Q

What frequencies appear what colour in visible light?

A

Lower frequencies appear more red and higher ones appear more blue as reds have the longest wavelengths and blues have the shortest wavelengths

37
Q

How do you know if an object’s emitting a lot of infrared radiation

A

It’s very hot

38
Q

What do all objects emit?

A

Infrared radiation

39
Q

Give an example where we can feel the effects of infrared?

A

When energy from the sun is transferred to our skin

40
Q

Give two similarities between infrared and UV radiation

A

They can both be detected by certain animals and they both can’t be detected by humans

41
Q

What did Herschel discover?

A

Infrared radiation

42
Q

How did Herschel make his discovery?

A

By putting thermometers at each colour of white light and then putting one beyond the red end of the visible light spectrum

43
Q

Why did Herschel think certain colours of visible light had different ‘amounts of heat’?

A

As while observing the sun, he found that different coloured filters heated up his telescope to different extents

44
Q

What is the order of the EM spectrum from lowest frequency to highest frequency

A

Radio waves, microwaves, infrared radiation, visible light, ultraviolet, x rays, gamma rays

45
Q

What is the frequency of visible light?

A

10^-6

46
Q

Why do scientists need to use different types of telescope to study different wavelengths from space?

A

As different materials effect em waves depending on the wavelength e.g. all gamma rays are absorbed by the atmosphere

47
Q

Why do most telescopes use curved mirrors?

A

To focus EM radiation onto a central sensor. Type of material and size of telescope depends on wavelength of radiation studied

48
Q

How does the atmosphere effect radio waves?

A

The ones with the shorter wavelengths aren’t absorbed by the atmosphere but the longer wavelengthed ones are

49
Q

What part of the em spectrum do our eyes detect?

A

Visible

50
Q

How is infared radiation used?

A
  • Short range communication e.g. tv remote
  • to heat food as it absorbs the radiation like in a grill/toaster
  • security systems with sensors that detect infrared emitted by intruders
51
Q

How are microwaves used?

A
  • For communication and satellite transmission like phone signals
  • to cook food in a microwave as they transfer energy to the food, heating it up
52
Q

How are radio waves used?

A
  • Communication like Transmission of radio broadcast and tv programs
  • satellite communication
53
Q

How does ground control communicate with spacecraft?

A

Using radio waves

54
Q

What are radio waves produced by?

A

Oscillations in electrical circuits

55
Q

What direction do waves travel?

A

Straight line unless reflected or refracted

56
Q

How are radio waves released and received?

A
  1. Current moves up and down a transmitting aerial
  2. Oscillations cause radio waves to spread out from the aerial
  3. Radio waves cause an oscillating current in the receiving aerial
57
Q

How does the ionosphere affect radio waves and microwaves?

A

It usually refracts radio waves back to earth if they are at a suitable angle and it transmits microwaves

58
Q

Why is there a maximum range for microwave communication?

A

As the curve of the earth surface gets in the way

59
Q

What is the ionosphere?

A

A region of charged particles in the atmosphere

60
Q

What’s the difference in terms of communication range between radio waves and microwaves?

A

Radio waves have a much greater communication distance than microwaves

61
Q

When does intensity of radiation emitted by an object increase?

A

As it’s temperature increases

62
Q

What’s the relationship between wavelengths of radiation and temperature?

A

The higher the temperature, the shorter the wavelength of radiation

63
Q

What is power and what is its unit?

A

The amount of energy transferred in a certain time and is measured in watts (w)

64
Q

What is needed for a system to stay at a constant temperature?

A

The system must absorb the same amount of power as it radiates

65
Q

How does the earth re radiate heat it absorbs from the sun?

A

as Infrared radiation

66
Q

What is the greenhouse effect?

A

Where gases in our atmosphere like carbon dioxide naturally absorb some energy keeping the earth at a higher temp.

67
Q

What use does uv light have?

A
  • Disinfect water by killing microorganisms

- used in fluorescence in security markings

68
Q

What is a fluorescent material? I

A

a materials that absorbs UV radiation and re emits it as visible light

69
Q

How do low energy light bulbs work as fluorescent lamps?

A

As a gas inside them produces uv radiation when an electrical current passes through it and a coating on inside the glass absorbs the uv and emits visible light

70
Q

How are x rays used?

A
  • to take images of inside the body
  • to examine inside of metal objects
  • to inspect luggage at airport security
71
Q

Why do medical x rays work?

A

As they can pass through muscles and fat easily but bone absorbs some x rays hence why they are visible in x ray scans

72
Q

What are the uses of gamma rays?

A
  • sterilise foods and surgical instruments
  • kill cancer cells in radiotherapy
  • detect cancer cells
73
Q

Why are gamma rays useful for sterlising surgical instruments and food, and killing cancer?

A

As they transfer a lot of energy and can kill cells

74
Q

How do gamma rays detect cancer cells?

A

A chemical that emits gamma rays is injected into the blood. It collects inside cancer cells and a scanner locates the scanner by finding the source of gamma rays

75
Q

Why couldn’t gamma rays produce images of inside the body like x rays?

A

As gamma rays pass through all materials in the body

76
Q

Why are phones safe for humans despite they emit microwaves?

A

As they use specific microwave frequencies that don’t effect our cells

77
Q

What can too much infrared do to humans?

A

Damage or destroy cells and cause burns to the skin

78
Q

Why is UV radiation dangerous?

A

It can cause sunburnt, damage to DNA and prolonged exposure could lead to skin cancer

79
Q

How do you protect yourself from the sun?

A

Where sun cream with high SPF, cover up with closing and hats and stay out of the strongest sunshine

80
Q

Give an example of the effects of UV radiation to or eyes.

A

Skiers and mountaineers can suffer temporary ‘snow blindness’ due to UV radiation reflecting from the snow

81
Q

Why are x rays and gamma rays most dangerous?

A

As they have the highest frequencies and shortest wavelengths

82
Q

What are the dangerous of x rays and gamma rays?

A

They may cause mutations in DNA that can kill cells or cause cancer

Physics Gcse (22 decks)

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