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Physics > Light And EM Spectrum > Flashcards

Light And EM Spectrum Flashcards

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1
Q

What types of waves are EM waves?

A

Transverse

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2
Q

What does EM stand for?

A

Electromagnetic

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3
Q

What is an EM wave?

A

A transverse wave caused by oscillations in an electromagnetic field.

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4
Q

What are the vibrations and oscillations in an EM wave?

A

They are the changes in electrical and magnetic fields at right angles to the direction of wave travel

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5
Q

What are the 3 things that all electromagnetic waves do?

A
  1. transfer energy as radiation
    from the source of the waves to an absorber
  2. can travel through a vacuum
    such as in space
  3. travel at the same speed through a vacuum or the air
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6
Q

How fast does an EM wave travel through a vacuum?

A

Electromagnetic waves travel at 300,000,000 metres per second (m/s) through a vacuum.

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7
Q

What do EM waves form?

A

A continuous spectrum of waves

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8
Q

What is a spectrum?

A

A series of similar waves arranged in order of wavelength or frequenc

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9
Q

What does the continuous
spectrum of waves formed by EM waves include?

A
  1. waves with a very short
    wavelength,high frequency and high energy
  2. waves with a very long wavelength, low frequency and low energy
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10
Q

What is wavelength?

A

The length of a single wave, measured from one wave peak to the next.

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11
Q

What is frequency?

A

The number of waves produced each second. The unit of frequency is hertz (Hz).

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12
Q

What are the 7 EM waves in order from longest to shortest

A

Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-ray
Gamma rays

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13
Q

What does an EM wave with a long wavelength also have?

A

Low frequency and low energy

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14
Q

What does an EM wave with a short wavelength also have?

A

High frequency
High energy

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15
Q

What does visible light contain?

A

the limited range of frequencies that can be detected by the human eye

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16
Q

What are the limited range of frequencies that can be seen by visible light, that can be detected by the human eye?

A

1.red light has the lowest frequencies of visible light
2.violet light has the highest frequencies of visible light

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17
Q

What does the behaviour of an EM wave in a substance depend on?

A

The frequency

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18
Q

What are radio waves used for?

A

communication such as broadcasting television and radio, communications and satellite transmissions.

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19
Q

Can radio waves be transmitted by air?

A

Radio waves are transmitted easily through air

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20
Q

Are radio waves damaging to us?

A

They do not cause damage if absorbed by the human body

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21
Q

Can radio waves be reflected?

A

they can be reflected to change their direction. These properties make them ideal for communications.

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22
Q

How can radio waves be produced?

A

Radio waves can be produced by
oscillations
in electrical circuits.

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23
Q

What happens when radio waves are absorbed by a conductor?

A

When radio waves are absorbed by a conductor
they create an
alternating current

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24
Q

What is a conductor?

A

A material which allows charge to move easily through it.

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25
Q

What is an alternating current?

A

Also called ac. An electric current that regularly changes its direction and size.

26
Q

What happens once a radio wave is absorbed by a conductor and made an alternating current?

A

This electrical current has the same frequency as the radio waves. Information is coded into the wave before transmission, which can then be decoded when the wave is received.

27
Q

How are TV and radio systems transmitted?

A

By an alternating current

28
Q

What are microwaves used for?

A

Microwaves are used for cooking food, communications and for satellite communications

29
Q

Are microwaves dangerous?

A

Intense sources of microwaves can be dangerous through internal heating of body cells.

30
Q

can high frequency microwaves be absorbed by food?

A

High frequency microwaves have frequencies which are easily absorbed by molecules in food

31
Q

What increases when food molecules absorb microwaves?

A

The
internal energy
of the molecules increases which causes heating

32
Q

What is internal energy?

A

The total kinetic energy and potential energy of the particles in an object.

33
Q

What can microwaves easily pass through? What does this mean?

A

Microwaves pass easily through the atmosphere, so they can pass between stations on Earth and satellites in orbit.

34
Q

What is infrared light absorbed by?

A

Infrared light has frequencies which are absorbed by some chemical bonds

35
Q

What happens to the internal bonds in a chemical when infrared light is absorbed?

A

The internal energy of the bonds increases when they absorb infrared light, which causes heating

36
Q

How is infrared light useful?

A

This makes infrared light useful for electrical heaters and for cooking food

37
Q

What do all object emit?

A

Infrared light

38
Q

Can the human eye see infrared light? And if not what can?

A

The human eye cannot see this light, but infrared cameras can detect it.

39
Q

What is thermal energy useful for?

A

This ‘thermal imaging’ is useful for detecting people in the dark.

40
Q

What is visible light used in and why?

A

Television and illumination because we can see them

41
Q

As well as television and illuminations what is visible light also used for?

A

is also used in fibre optic communications,

42
Q

How does fibre optic communications work?

A

It’s where coded pulses of light travel through glass fibres from a source to a receiver.

43
Q

Can we see ultraviolet?

A

No

44
Q

Is UV dangerous?

A

It can have hazardous effects on the human body

45
Q

What causes us to can or burn?

A

The ultraviolet light in the sun

46
Q

What are fluorescent substances used in?

A

energy-efficient lamps

47
Q

How is UV used in energy efficient lamps?

A

they absorb ultraviolet light produced inside the lamp, and re-emit the energy as visible light

48
Q

How is UV used on bank notes?

A

Similar substances are used on bank notes to detect forgeries.

49
Q

What does The hazardous properties of UV mean it will kill?

A

Bacteria-so it can be used for disinfecting water

50
Q

What can cause electromagnetic waves to be generated or absorbed?

A

Changes in atoms and their nuclei

51
Q

How are gamma rays produced?

A

Gamma rays are produced by changes in the nucleus of an atom

52
Q

What are gamma rays a form of?

A

Nuclear radiation

53
Q

What are High energy waves such as X-rays and gamma rays are transmitted through?

A

body tissues with very little absorption.

54
Q

What does the very little absorption by the body tissues mean that gamma is useful for?

A

for internal imaging. X-rays are absorbed by dense structures like bones, which is why X-ray photos are used to help identify broken bones.

55
Q

What are x rays used for?

A

used to help identify broken bones.
X-scanning the internal structure of objects
in airport security scanners.

56
Q

What are gamma rays used for?

A

are used for sterilising food and medical instruments, and in the treatment and detection of cancer.

57
Q

What 3 waves are types of ionising radiation?

A

Ultraviolet waves, X-rays and gamma rays

58
Q

What is ionising radiation?

A

Radiation that is able to remove electrons from atoms or molecules to produce positively charged particles called ions.

59
Q

What can ionising radiation do to the body?

A

Ionisation can have hazardous effects on the body

60
Q

How can UV light harm the body?

A

Ultraviolet waves can cause damage to skin cells and eyes, and increase the risk of skin cancer

61
Q

How can x-rays harm the body?

A

X-rays and gamma rays can cause the mutation of genes, which can lead to cancer

Physics (12 decks)

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