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Physics > Unit 5 - Light And The Electomagnetic Spectrum > Flashcards

Unit 5 - Light And The Electomagnetic Spectrum Flashcards

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1
Q

What is a ray diagram?

A

A diagram that shows what happens when light is reflected or refracted.

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2
Q

What is the normal?

A

A line drawn at a right angle to the barrier

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3
Q

What is the incident ray and the reflected ray measured from?

A

The normal

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4
Q

What waves can be used to also see what happens to light

A

Water waves as they work the same way when they hit a barrier

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5
Q

What is the law of refraction.

A

The angle of refraction is equal to the angle of incidence.

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6
Q

What is refraction

A

When a ray of light moves into a material where it travels at a different speed as it is of a different density

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7
Q

What is the interface

A

The boundary that a light ray meets when it refracts

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8
Q

Why might there be no refraction

A

If the light meets the interface at a right angle

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9
Q

What is total internal reflection

A

When the light is completely reflected inside the glass

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10
Q

What is the critical angle

A

The angle when the reflected light passes along the interface of the glass block

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11
Q

What shape is the glass block need to be in order for total internal reflection to happen

A

Semi circular glass block

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12
Q

In a semi circular glass block, what happens if the angle of incidence is less than the critical angle

A

The small amount of light is reflected most is refracted

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13
Q

What happens if the angle of incidence in a semi circular glass broke is greater than the critical angle

A

All of the light is completely reflected inside the block

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14
Q

Explain the core practical – investigating refraction

A

Put a piece of paper on my desk and set a power supply, ray box with a single slit. Put a rectangular glass block on the paper and draw around it. Shine a ray of light onto the block and marks small crosses where the rays go. Take off the block and join the crosses using a ruler to show the path. Join the points from where it entered and left the plot to show the path of inside the block. Measure the angles of incidence and refraction using a normal. If it is at a right angle, nothing will happen. Repeat with different angles.

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15
Q

What is different between seeing luminous and nonluminous objects

A

With luminous objects, the light from them enters your eye. With nonluminous object, the reflected light enters your eye

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16
Q

What is diffuse reflection

A

When the light is scattered directions from a rough surface

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17
Q

What is specular reflection

A

When light is reflected evenly from a very smooth surface such as mirrors

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18
Q

What is white light

A

Light made up of a mixture of colours that we see as white.

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19
Q

What light comes from the Sun or lamps

A

White light

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20
Q

What is the visible spectrum

A

When whites light splits up into different colours using a prism

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21
Q

How do we see coloured objects

A

Objects of a colour reflects the same colour of this visible spectrum. The rest of the colours are absorbed

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22
Q

How do we see white light

A

The objects reflects all of the colours

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23
Q

What are filters

A

Pieces of transparent material that absorb some of the colours white light but transmitting a specific colour.

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24
Q

What is a lens

A

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

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25
Q

A more powerful lens means…

A

The light bends more

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26
Q

What is a converging lens

A

A lens that is fatter in the middle. This makes parallel rays of light converge at a focal point. The focal point is after the lens

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27
Q

What is the focal length

A

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

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28
Q

What is a diverging lens

A

A lens that is thinner in the middle then at the edges and dispersers parallel rays of light. The focal point is in front of the lines as if the dispersed rays of light join at a particular point, it would be in front

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29
Q

What is a real image

A

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

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30
Q

How is a real image formed

A

The object must be further away from the lens than the focal point. When the light rays are refracted using the converging lens a real image is formed. This can be projected onto a screen

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31
Q

How is a virtual image formed

A

The object must be closer to the loans than the focal point. The race that point into the eye after they have been reflected by the lines all point to the focal point where a virtual image is formed. This is formed as if there wasn’t a lens and is the virtual image.

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32
Q

Give an example of a converging lens to form a virtual image

A

Magnifying glass

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33
Q

What does a virtual image look like

A

Upright and bigger

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34
Q

What does a real object look like

A

Upside down and smaller than the object

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35
Q

What do diverging lenses produce

A

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

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36
Q

What is visible light

A

A part of the electromagnetic spectrum that we can see as our eyes can detect a certain frequency

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37
Q

What do you lower frequencies of visible light appears as

A

More red

38
Q

What do high frequencies of visible light appear as

A

More blue

39
Q

What is ultraviolet

A

Electromagnetic waves with frequency of the little higher than visible light

40
Q

What type of wave are electromagnetic waves

A

Transverse, the electromagnetic vibrations are at right angles to the direction the energy is being transferred

41
Q

What speed do all electromagnetic waves travel at in a vacuum

A

3 x 10^8 m/s

42
Q

What is infrared

A

Electromagnetic waves with frequency is slightly lower than visible light

43
Q

What is infrared also known as

A

Heat

44
Q

Who was the first person to investigate infrared radiation

A

William Herschel

45
Q

What did William Herschel do

A

He used dark coloured filters on his telescope to help him see the sun safely. He noticed that different colours heated up the telescope different amounts. He wanted to test his idea is that different colours of light contained different amounts of heat so he split sunlight into a spectrum using a prism and put a thermometer in each of the colours and measured the temperature just beyond the red which was infrared

46
Q

What are the seven colours in the visible light spectrum

A

Red, orange, yellow, green, blue, Indigo and violet

47
Q

What electromagnetic waves have a lower frequency than visible light

A

Infrared, microwaves and radio waves

48
Q

What electromagnetic waves have a higher frequency than visible light

A

Ultraviolet, x-rays, gamma rays

49
Q

What is the electromagnetic spectrum

A

The full range of electromagnetic waves

50
Q

How big are the waves if they have a high frequency

A

Very short

51
Q

Why do astronomers use different kinds of telescope to study different wavelengths

A

Different materials affect electromagnetic waves depending on the wavelength

52
Q

Why do most telescope use curved mirrors

A

To focus the electromagnetic radiation onto a central sensor

53
Q

What is visible light used for

A

Lightbulbs and cameras protect it and record images

54
Q

Give three uses of infrared

A

Short range communication such as a TV to its remote control
Grills or toasters
Security systems that have infrared sensors

55
Q

Give two uses of microwaves

A

Communication and satellite transmissions including mobile phones.
Microwave oven to heat up food

56
Q

What are radio waves used for (2)

A

Transmitting radio broadcasts and TV programmes

Controllers on the ground communicating with spacecraft

57
Q

What are oscillations

A

Variations in current and voltage

58
Q

How are radio waves produced?

A

By oscillations in electrical circuits

59
Q

How do aerials work

A

Aerials are metal rods that absorb radio waves. A transmitting aerial has current moving up and down. These oscillations cause radio waves to spread out from the aerial. The radio waves cause an oscillating current in the receiving aerial.

60
Q

What layer in the atmosphere can refract some frequencies of radio waves

A

Ionosphere

61
Q

What is the ionosphere

A

Region of charged particles in the atmosphere

62
Q

Which out of radio waves and microwaves has a greater range

A

Radio waves

63
Q

Why might some radio waves be sent back towards the Earth

A

If they reach the ionosphere at a suitable angle, they may be reflected enough.

64
Q

Can microwaves be reflected in the earths atmosphere

A

No

65
Q

If there is a high temperature, how long will the wavelength be

A

Shorter

66
Q

Which part of lavar is the hottest

A

Yellow

67
Q

What is the power

A

The amount of energy transferred in a certain time measured in watts

68
Q

How can a system stay at a constant temperature

A

It must absorb the same amount of power as it radiates

69
Q

How does the Earth re-radiate the energy from the Sun

A

As infrared radiation

70
Q

What are greenhouse gases

A

Gases and all atmosphere that naturally absorb some energy

71
Q

What is the greenhouse effect

A

When greenhouse gases absorb the energy keeping the earth at a higher temperature then if there were no atmosphere

72
Q

Explain the core practical – investigating radiation

A

Cover for boiling tubes in different coloured materials.
Pour same volume of hot water from a kettle in each tube
Insert a bung with a thermometer into each tune and measure the temperature every 2 minutes for 20 minutes.
Record temperatures

73
Q

What transfers more energy: visible light or ultraviolet radiation

A

Ultraviolet radiation

74
Q

How can ultraviolet be used to disinfect water

A

If water in plastic bottles are placed in the sunshine for several hours the infrared energy from the Sun will heat the water up enough so that’s the ultraviolet radiation will help to kill microorganisms

75
Q

What is fluorescence

A

When materials absorb ultraviolet radiation and re-emit it as visible light

76
Q

What are fluorescent materials used in

A

Security markings as they are only visible when ultraviolet light shines on them

77
Q

Ultraviolet in low energy lightbulbs

A

These low energy lightbulbs are fluorescent. A gas inside them produces ultraviolet radiation when an electrical current passes through it. A coating inside the glass absorbs the ultraviolet and emits visible light

78
Q

Why can x-rays be used in medicine to make images of inside the body

A

X-rays can pass through many materials that visible light cannot however bone absorbs some x-rays which creates the bone image

79
Q

Apart from medicine what can x-rays also be used for

A

Airport security to inspect luggage and metal objects

80
Q

Why my gamma rays be used to sterilise food and surgical instruments

A

Because they transfer a lot of energy which can kill harmful microorganisms and other cells

81
Q

What is radiotherapy

A

The process where gamma rays are used to kill cancer cells

82
Q

How can gamma rays be used to detect cancer

A

A chemical that emits gamma rays is injected into the blood which is designed to collect inside cancer cells. A scanner outside the body locate the cancer by finding the source of the gamma rays

83
Q

Why might microwaves be dangerous to Our bodies

A

A certain microwave frequency can heat water inside our cells which may cause them to burst

84
Q

Why are microwaves use in mobile phones not dangerous

A

They use a different frequency that are not a health risk

85
Q

What is a danger of infrared radiation

A

It can damage or destroy cells causing burns to the skin

86
Q

Give 5 dangers of ultraviolet radiation

A

It can cause sunburn, damage the DNA, skin cancer, cataracts and damage to our eyes (skiers and mountain is cancer for temporary snow blindness from too much ultraviolet radiation reflected from snow)

87
Q

Give 2 dangers of x-rays and gamma rays

A

They can penetrate the body and excessive exposure can cause mutations in the DNA that can kill cells or cause cancer

88
Q

How is electromagnetic radiation produced

A

By the changes in the electrons or the nuclei in atoms

89
Q

Give an example of how infrared and gamma radiation can be produced

A

When materials are heated the formation of electrons can change which can produce infrared radiation. Changes in the nuclei of atoms can produce gamma radiation

90
Q

How can the constant temperature of the earth change

A

When greenhouse gases are added they absorb more energy making the temperature rise. The greenhouse gases can only absorb a certain amount and after that the Earth will return to radiating the same power as they receive

Physics (12 decks)

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