# P6:Waves Flashcards

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1
Q

When waves travel through a medium, the particles of the medium…

A

Oscillate and transfer energy between each other, but overall, the particles stay in the same place - only energy is transferred

2
Q

The amplitude is a wave is the maximum…

A

Displacement of a point in the wave from its undisturbed position

3
Q

The wavelength is the distance between the same point on…

A

Two adjacent waves. (EG: between the trough of one wave and the trough of the wave next to it)

4
Q

Frequency is the number of complex waves passing a…

A

Certain point per second, frequency is measured in hertz (Hz). 1 Hz is 1 wave per second

5
Q

From the frequency, you can find the period of a wave using the amount of time it takes for a full cycle of the wave…

A
```T = 1/F
Period(s) = 1 / Frequency(Hz)```
6
Q

Transverse waves have sideways vibrations. In transverse waves, the oscillations are perpendicular (at 90*) to the direction of energy transfer.

A
• All electromagnetic waves
• Ripple and waves in water
• A wave on a string
7
Q

Longitudinal waves have parallel vibrations…

A

In longitudinal waves, the oscillations are parallel to the direction of energy transfer. For example, sound waves in the air

8
Q

The wave speed is the speed at which energy is being transferred or…

A

The speed the wave is moving at

9
Q

Wave equation…

A
```V = F x λ
Wave speed(m/s) = frequency(Hz) x wavelength(m)```
10
Q

All waves can be…

A

Absorbed, transmitted or reflected, this occurs when a wave meets a boundary between two materials

11
Q

The wave is absorbed by the second material…

A

The wave transfers energy to the materials energy stores. Often, the energy is transferred to a thermal energy store, which leads to heating. For example, a microwave

12
Q

The wave is transmitted through the second material…

A

The wave varies in travelling through the new material. This often leads to refraction. This can be used in communications as well as in the lenses of glasses and cameras

13
Q

The wave is reflected…

A

This is where the incoming ray is neither absorbed or transmitted but instead it returned away from the second material. This is how echos are created

14
Q

Whether the wave is absorbed, transmitted or reflected depends on…

A

The wavelength of the wave and the properties of the materials involved

15
Q

Electromagnetic waves are…

A

Transverse waves, they transfer energy from a source to an absorbed

16
Q

A campfire transfers energy to its surroundings by emitting infrared radiation…

A

These infrared waves are absorbed by objects and transfer energy to the objects thermal energy store, causing the object to warm up

17
Q

Radio waves transfers energy to the kinetic energy stores of…

A

18
Q

All EM waves travel at the same speed through the air or a vacuum…

A

EM waves aren’t vibrations of particles, they’re vibrations of electric and magnetic fields. This means they can travel through a vacuum. They travel at different speeds in different materials which can lead to refraction

19
Q

A vacuum is another name for…

A

A space

20
Q

EM waves vary in wavelength from around 10(^-15)…

A

To more than 10(^4)

21
Q

We group waves based on their wavelength and frequency…

A

There are seven basic types, but the different groups merge to form a continuous spectrum

22
Q

Our eyes can only detect a small part of the electromagnetic spectrum…

A

Visible light

23
Q

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays

A

Long wavelength, low frequency to short wavelength, high frequency

24
Q

There is such a larger range of frequencies because EM waves are…

A

Generated by a variety of changes in atoms and their nuclei. For example, changes in the nucleus of an atom creates gamma rays. Also explaining why atoms can absorb a range of frequencies, each one causes a different change

25
Q

Because if their different properties…

A

Different EM waves are used for different purposes

26
Q

When EM radiation enters living tissue…

A

It’s often harmless, but it can sometimes creates havoc, the effects of each type of radiation are based on how much energy the wave transfers

27
Q

Low frequency waves, like radio waves…

A

Don’t transfer much energy and so mostly pass through soft tissue without being absorbed

28
Q

High frequency waves like UV, X-rays and gamma rays all transfer…

A

Lots of energy and so can cause lots of damage

29
Q

UV radiation damages surface cells, which can lead to sunburn and cause skin to…

A

Age prematurely, some more serious effects are blindness and an increased risk of skin cancer

30
Q

X-rays and gamma rays are types of ionising radiation…

A

This can cause gene mutation or Bell destruction and cancer

31
Q

A

They carry enough energy to knock electrons off of atoms

32
Q

Whilst UV radiation, X-rays and gamma rays can be harmful, they are also very useful…

A

Before any of these types of EM radiation are used, people look at whether the benefits outweigh the health risks

33
Q

The risks of a person involved in a car accident developing cancer from having an X-ray photograph taken is…

A

Much smaller than the potential health risk of not finding and treating their injustices

34
Q

Radiation dose (measured in sieverts) is a measure of the risk of…

A

Harm from the body being exposed to radiation, this isn’t however a measure of the total amount of radiation that has been absorbed

35
Q

The risk depends on the total amount of radiation absorbed and…

A

How harmful the type of radiation is

36
Q

A sievert is pretty big, so you’ll often see diesel in…

A

Millisieverts (mSv), where 1000 mSv = 1 Sv

37
Q

Risks can be different for different parts of the body…

A

A CT scan uses X-rays and a computer to build up a picture of inside the patients body. The radiation dose to the persons head is 2.0mSv and to the chest is 8.0mSv. If a patient has a CY scam on their chest, they are four times more likely to suffer damage to their genes (and their added risk of harm is 4x higher) than I they had a head scan

38
Q

Optical fibres are thin glass or plastic fibres that can carry data (E.G: from telephone or computers)…

A

Over long distances as pulses of visible light. They work because of reflection, the light rays are bounced back and forth until they reach the end of the fibre

39
Q

Visible light is sided in optical fibres because it is easy to refract light enough so that it…

A

Remains in a narrow fibre, light is also not easily absorbed or scattered as it travels along a fibre

40
Q

Fluorescence is a property of certain chemicals where…

A

UV radiation is absorbed and then visible light is emitted. That’s why fluorescent colours look so bright, they actually emit light

41
Q

Fluorescent lights generate UB radiation, which is absorbed and re-emitted as visible light by a layer of…

A

Phosphorus on the inside of the bulb. They’re energy efficient so they are good to use when light is needed for long periods

42
Q

Security pens can be used to mark property with your name….

A

Under UV light the ink will glow (fluoresce), but it’s invisible otherwise. This can help the police identify your property if it’s stolen

43
Q

UB is produced by the sun…

A

Exposure to it is what gives people suntan

44
Q

When it’s not sunny, some people go to tanning salons where UV lamps are used to give them an artificial suntan. However…

A

Overexposure to the UV radiation can be dangerous (fluorescent lights emit very little UV, so they’re say)

45
Q

Radiographers in hospitals take X-rays ‘photographs’ of people to…

A

See if they have any broken bones

46
Q

X-rays pass easily through the flesh but not so easily through denser material…

A

Like bones or metal. So it’s the amount of radiation that’s absorbed (or not absorbed) that gives you an X-ray image

47
Q

Radiographers use X-rays and gamma rays to treat people with cancer (radiotherapy)…

A

This is because high doses of these rays kill all living cells, so they are carefully directed towards cancer cells, to avoid killing too many normal, healthy cells

48
Q

Gamma radiation can also be used as a medical tracer…

A

This is where a gamma emitting source is injected into the patient, and it’s progress is followed around the body. Gamma radiation is well suited to this because it can pass through the body to be detected

49
Q

Both X-rays and gamma rays can be harmful to people, so radiographers wear…

A

Lead aprons and stand behind lead screens or leave the room to keep their exposure to them to a minimum

50
Q

A

51
Q

Long-wave radio (wavelengths of 1-10KM) can be transmitted from ldn and received…

A

Half way around the world. That’s because long wavelengths diffract around the curved surface of the earth, the can also diffract around hill and into tunnels.

52
Q

Definition of diffract…

A

Bend

53
Q

Long-wave radio makes it possible for…

A

Radio signals to be received even if the receiver isn’t in line if the sight of the transmitter

54
Q

Short-wave radio signals (wave lengths of about 10m - 100m) can be…

A

Received at long distances from the transmitter. That’s because they are reflected, from the ionosphere - an electrically charged later in the Earths upper atmosphere

55
Q

Bluetooth uses…

A

Short-wave radio waves to send data over short distances between devices without wires

56
Q

Medium-wave signals can also…

A

Reflect from the ionosphere, depending on atmospheric conditions and the time of day

57
Q

The radio waves used for TV and FM radio transmissions have very short wavelengths…

A

To get receptions you must be in direct sight of the transmitter, the signal doesn’t bend or travel far through building

58
Q

Communications to and from satellites…

A

Uses microwaves, but you need to use microwaves which can easily pass through the earths watery atmosphere

59
Q

For satellite Tv, the signal from the transmitter is transmitted into space…

A

Where it’s picked up by a satellite receiver dish orbiting around the earth. The satellite transmits the signal back to the Earth in a different direction. Where it’s received by a satellite dish on the ground

60
Q

There is a slight time delay between…

A

The signal being sent and received because of the long distance the signal has to travel

61
Q

In microwave ovens, the microwaves need to be absorbed by water molecules in food…

A

So they can use a different wavelength to those used in satellite communications

62
Q

Microwaves penetrate up to a few cm into the food before being absorbed and transferring the energy they are carrying to the…

A

Water molecules in the food, causing the water to heat up. The water molecules the transfer this energy to the rest of the molecules in the food by heating, which quickly cooks the food

63
Q

Infrared (IR) radiation is given out by all objects…

A

The hotter the object, the more IR radiation it gives out

64
Q

Infrared cameras can be used to detect infrared radiation and monitor temp….

A

The camera detects the IR radiation and turn it into an electrical signal, which is displayed on a screen as a picture, the hotter an object is the brighter it appears

65
Q

Absorbing IR radiation causes objects to get hotter…

A

Food can be cooked using IR radiation, the temperature of the food increased when it absorbs IR radiation

66
Q

Electric heaters contain a long piece of wire that what’s up when a current flows through it, this wire emits lots of IR and a little bit of visible light (the wire glows)….

A

The emitted IR radiation is absorbed by objects and the air in the room, energy is transferred by the IR waves to the thermal energy stores of the objects, causing the temperature to increase

67
Q

If the wave is travelling along the normal

A

It will change speed, but it’s NOT refracted

68
Q

The wavelength of a wave changes when it’s refracted, but…

A

The frequency stays the same

69
Q

You can produce radio waves using an alternating current in an electrical circuit…

A

The object in which charges (electrons) oscillate to create the radio waves is called a transmitter

70
Q

Rays are straight lines that are perpendicular to wave fronts…

A

They show the direction a wave is travelling in

71
Q

Construction of a ray diagram for a refracted light ray…

A
• Draw the boundary between your two materials and the normal
• Draw an incident ray that meets the normal at the boundary
• The angle between the incident ray and the normal is the angle of incidence
• Now Draw the refracted ray in the other side of the boundary
• The angle of refraction is the angle between the refracted ray and the normal