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GCSE - Physics > Topic 6 > Flashcards

Topic 6 Flashcards

(73 cards)

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1
Q

What do waves do?

A

Transfer energy in the direction they are travelling

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2
Q

What happens when a wave travels through a medium?

A

The particles of the medium oscillate and transfer energy between each other. BUT overall, the particles stay in the same place - only energy is transferred.

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3
Q

What is the amplitude of a wave?

A

its the maximum displacement of a point on the wave from its undisturbed position

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4
Q

What is the wavelength of a wave?

A

The wavelength is the distance between the same point on two adjacent waves.

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5
Q

What is frequency in waves?

A

The number of complete waves passing a certain point per second

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6
Q

What is frequency measured in?

A

Hz or hertz

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7
Q

What does 1Hz equal?

A

1Hz is 1 wave per second

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8
Q

What is a period of a wave?

A

The amount of time it takes for a full cycle of the wave.

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9
Q

How do you work out a period of a wave?

A

period (s) = 1
_________
frequency (Hz)

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10
Q

What types of waves are there?

A

Transverse or longitudinal.

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11
Q

Describe the vibrations of transverse waves.

A

In transverse waves, the oscillations (vibrations) are perpendicular (sideways at 90 degrees) to the direction of energy transferred.

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12
Q

Give some examples of transverse waves.

A

-all electromagnetic waves e.g light
-ripples and waves in water
-a wave on a string

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13
Q

Describe the vibrations of longitudinal waves.

A

In longitudinal waves, the oscillations (vibrations) are parallel to the direction of energy transferred.

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14
Q

Give some examples of longitudinal waves.

A

-sound waves in air, ultrasound
-shock waves e.g some seismic waves

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15
Q

What is the wave speed?

A

the speed at which energy is being transferred or the speed the wave is moving at.

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16
Q

How do you calculate wave speed?

A

wave speed (m/s) = frequency (Hz) x wavelength (m)

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17
Q

What can you use to measure the speed of sound?

A

oscilloscope

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18
Q

What can you use to find the wavelength of the sound waves generated?

A

-2 microphones
-an oscilloscope

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19
Q

Explain what you would do to find the wavelength of the sound waves generated?

A

1)set up the oscilloscope so the detected waves each microphone are shown as separate waves
2)start with both microphones next to the speaker, then slowly move one away until the two waves are aligned on the display, but have moved exactly one wavelength apart
3)Measure the distance between the microphones to find one wavelength
4)You can then use the formula wave speed = frequency x wavelength to find the speed (v) of the sound waves passing through the air
5)The speed of sound in air is roughly 330 m/s, so check your results roughly agree with this

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20
Q

What can happen to waves?

A

Waves can be absorbed, transmitted or reflected

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21
Q

What is a wave absorbed by and what happens when a wave is absorbed?

A

The wave is absorbed by the material the wave is trying to cross into - this transfers energy into the material’s energy store

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22
Q

What happens when a wave is transmitted?

A

The waves carry on travelling through the new material. This often leads to refraction.

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23
Q

Where are waves reflected at?

A

At different boundaries in different ways

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24
Q

When does a specular reflection happen?

A

When a wave is reflected in a single direction by a smooth surface.

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25
What is diffuse reflection?
When a wave is reflected by a rough surface and the reflected rays are scattered in lots of different directions. This happens because the normal is different for each incoming ray, which means that the angle of incidence is different for each ray. The rule of angle of incidence = angle of reflection still applies.
26
What happens when light is reflected by a rough surface?
The surface appears matte (not shiny) and you don't get a clear reflection of objects.
27
What is the rule you need to know for all reflected waves?
angle of incidence = angle of reflection
28
What is the angle of incidence?
The angle between the incoming wave and the normal
29
What is the angle of reflection?
The angle between the reflected wave and the normal
30
What is the normal?
An imaginary line that's perpendicular (at the right angles) to the surface at the point of incidence ( the point where the wave hits the boundary). The normal is usually shown as a dotted line.
31
What is the point of incidence?
The point where the wave hits the boundary.
32
What type of wave is all EM waves?
transverse waves that transfer energy from a source to an absorber
33
At what speed do EM waves travel through air or a vacuum (space)?
All EM travel at the same speed through air or a vacuum (space).
34
What do electromagnetic waves form?
A continuous spectrum over a range of frequencies
35
State the groups in order that electromagnetic waves are grouped in based on wavelength and frequency.
radio waves micro waves infra red visible light ultra violet x rays gamma rays
36
What does how much a wave is refracted by depend on?
how much the wave speeds up or slows down, which usually depends on the density of the two materials (usually the higher the density of a material, the slower a wave travels through it).
37
What happens when a wave slows down?
it will bend towards the normal
38
What changes and stays the same as a wave is refracted?
The wavelength changes but the frequency stays the same.
39
What happens when the wave is travelling along the normal?
It will change speed but it's not refracted.
40
What is the optical density of a material?
The optical density of a material is a measure of how quickly a light can travel through it - the higher the optical density, the slower light waves travel through it.
41
What are all EM waves made up of?
Oscillating electric and magnetic fields
42
What are alternating currents made up of?
oscillating charges. As the charges oscillate, they produce oscillating electric and magnetic fields
43
How can you produce radio waves?
You can produce radio waves using an alternating current in an electrical circuit.
44
What is a transmitter?
The object in which charges (electrons) oscillate to create the radio waves
45
What happens when a transmitted radio waves reach a receiver?
The radio waves are absorbed. The energy carried by the waves is transferred to the electrons in the material of the receiver. This causes the electrons to oscillate and if the receiver is part of a complete electrical circuit it generates an alternating current. This current has the same frequency as the radio wave that generated it.
46
What are radio waves mainly used for?
communication
47
Why can long - wave radio (wavelengths of 1-10km) be transmitted from London and received halfway across the world?
Because long wavelengths refract (bend) around the curved surface of the earth. This makes it possible for radio signals to be received even if the receiver isn't in the sight of the transmitter
48
Why can short - wave radio signals be received at long distances from the transmitter?
That's because they are reflected from the ionosphere - an electrically charged layer in the earths upper atmosphere.
48
What are long - wave radio signals?
wavelengths of 1-10km
49
What is the ionosphere?
An electrically charged layer in the earths upper atmosphere.
50
What can medium wave signals be reflected from?
the ionosphere (an electrically charged layer in the earths upper atmosphere) depending on atmospheric conditions and the time of day.
51
What are microwaves used by?
Satellites. But you need to use microwaves that can pass easily through the earths watery atmosphere
52
What do microwave ovens use?
A different wavelength from satellites. The microwave needs to be absorbed by water molecules in food - so they use a different wavelength to those used in satellite communications.
53
How do microwave ovens use microwaves to quickly cook the food?
The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to the 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 cook the food.
54
What can infrared radiation be used for?
To increase or monitor temperature
55
What is infrared radiation given out by?
all hot objects - the hotter the object the more infrared radiation it gives out
56
What can infrared cameras be used for?
detecting infrared radiation and monitor temperature. The camera detects the IR radiation and turns it into an electrical signal, which is displayed on a screen as a picture. The hotter an object is the brighter it appers.
57
What does absorbing infrared radiation cause?
it cause objects to get hotter infrared radiation can cause food to be cooked - the temperature off food increases when it absorbs IR radiation.
58
How do electric heaters heat a room?
Electric heaters contain a long piece of wire that heat up when a current flows through it. This wire then emits lots of infrared radiation (and a little visible light - the wire glows). The emitted IR radiation is absorbed by objects and the air in the room - energy is transferred from the IR waves to the thermal energy store of the objects, causing their temperature to increase.
59
What are optical fibres?
Thin glass or plastic fibres that can carry data over long distances as pulses of visible light.
60
What do fibre optic cables use to transmit data?
Visible light
61
Why do optical fibres work?
because of reflection. the light rays are bounced back and forth until they reach the end of the fibre.
62
What happens to light as it travels along a fibre?
- light rays bounce back and forth along the fibre -light is not easily absorbed or scattered
63
What is Fluorescence?
Fluorescence is a property of certain chemicals, where ultra-violet (UV) radiation is absorbed and then visible light is emitted. That's why Fluorescence colours look so bright - they actually emit light.
64
What do Fluorescence lights generate?
Fluorescence lights generate ultra-violet (UV) radiation, which is absorbed and re-emitted as visible light by a layer of phosphorus on the inside of the bulb. They're energy-efficient so they're good to use when light is needed for long periods.
65
What can security pens be used for?
To mark property with your name. Under UV light the ink will glow (fluoresce) but its invisible otherwise. This can help the police identify your property if its stolen.
66
What is ultra-violet (UV) radiation produced by?
the sun and exposure to it will give people a sun tan.
67
What are x-rays and gamma rays used in?
Medicine
68
What are x-rays used for in medicine?
Radiographers in hospitals take x-ray 'photographs' of people to see if they have any broken bones. X-rays pass easily through flesh but not so easily through denser material like bones or metal. So it the amount of radiation that's absorbed (or not absorbed) that gives you an x-ray image.
68
What do radiographers use x-rays and gamma rays to treat?
people with cancer (radiotherapy). This is because high doses of these rays kill all living cells - so they are carefully directed towards cancer cells, too avoid killing too many normal, healthy cells
69
What can gamma radiation be used for?
medical tracer - this is where a gamma-emitting source is injected into the patient and its progress is followed around the body. Gamma radiation is well suited to do this because it can pass out through the body to be detected.
70
What are some cons of both gamma and x-rays?
They can be harmful to people, so radiographers wear lead aprons and stand behind a lead screen or leave the room to keep their exposure to them to a minimum
71
When can EM radiation waves be harmful?

GCSE - Physics (8 decks)

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