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Physics GCSE > P12/P13 > Flashcards

P12/P13 Flashcards

1
Q

What are sound waves, water waves, waves on springs and ropes, and seismic waves (produced by earthquakes)?

A

Mechanical waves- whcih are vibrations that travel through a medium (substance)

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2
Q

What are light waves, radio waves, and microwaves all examples of?

A

Electromagnetic waves, which can all travel through a vacuum at the same speed of 300000 km per second. No medium is needed.

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3
Q

What happens when waves travel through a medium?

A

They oscillate and transfer energy between each other but do not move, only energy is transferred.

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4
Q

Describe a transverse wave in relation to oscillations?

A

In transverse waves, the oscillations (vibrations) are perpendicular (90°) to the direction of energy transfer.

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5
Q

3 examples of transverse waves?

A

= All electromagnetic waves e.g. light
= a wave on a string
= ripples and waves in water

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6
Q

Describe longitudinal waves in relation to oscillations?

A

In longitudinal waves, the oscillations are parralel to the direction of energy transfer

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7
Q

2 examples of longitudinal waves:

A

= sound waves in air, ultrasound
= shock waves e.g. seismic waves

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8
Q

What is wave speed?

A

Wave speed is the speed at which energy is being transferred ( or the speed a wave is moving at).

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9
Q

Page 73 Diagram and paragraph about it missing

A
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10
Q

What is frequency?

A

The number of waves passing a fixed point every second is called the frequency of the waves.

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11
Q

What three things happen when waves arrive at a boundary with two materials either side?

A

:::: waves are absorbed by the material the wave is trying to cross into - transfering energy to the materials energy stores

::: waves are transmitted - the waves carry on travelling through the new material. Often leading to refraction

::: the waves are reflected

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12
Q

What is the rule for all reflected waves?

A

Angle of incidence = Angle of reflection

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13
Q

What is the angle of incidence and the angle of reflection?

A

:::Angle of incidence is the angle between the incoming wave and the normal

:::Angle of reflection is the angle between the reflected wave and the normal

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14
Q

What is the normal is a ray diagram?

A

The normal is an imaginary line that’s perpendicular to the surface at the point of incidence. Usually a dotted line

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15
Q

What is specular reflection?

A

Specular reflection happens when a wave is reflected in a single direction by a smooth surface.

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16
Q

What is diffuse reflection?

A

Diffuse reflection is when a wave is reflected by a rough surface and 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 STILL = THE ANGLE OF REFLECTION.

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17
Q

What happens whenlight is reflected on a rough surface?

A

The surface appears matte (not shiny) and you don’t get a clear reflection of objects.

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18
Q

What is a wave?

A

A wave is a transfer of energy from one point to another. A wave transports energy not matter

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19
Q

What happens when a wave crosses a boundary between materials at an angle? If it refracts, how much by?

A

It changes direction - it refracts

How much its refracted by depends on how much the wave speeds up or slows down, which usually depends on the density of the materials (higher density of material, slower it travels usaully).

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20
Q

What happens if a wave crosses a boundary/ into a material and slows down/speeds up?

A

If a wave crosses a boundary and it slows down it will bend towards from the normal.
If it crosses into a material and speeds up it will bend away from the normal.

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21
Q

What happens when a wave is refracted?

A

The wavelength of a wave changes when it is refracted, but the frequency stays the same.

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22
Q

What happens when the wave is travelling at the normal into a boundary/material?

A

It wll change speed, but not refract

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23
Q

How are sound waves caused?

A

They are caused by vibrating objects. These vibrations are passed through the surrounding medium as a series of compressions and rarefactions.

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24
Q

What type of wave is a sound wave

A

Its a longitudinal wave.

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25
Q

What does sound travel faster in and what does it do when travelling in a solid?

A

Faster in solids than in liquids, and faster in liquids than in gases.
When travelling in a solid it does it by causing the particles in the solid to vibrate

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26
Q

Why can’t sound travel through space?

A

Because it is a vaccum so theres no particles for sound to move or vibrate.

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27
Q

Describe the process of sensing or hearing sound?

A

(1) sound waves that reach your ear drum can cause it to vibrate

(2) these vibrations are passed on to tiny bones in your ear called OSSICLES, through the SEMICIRCULAR CANALS and to the COCHLEA.

(3) COCHLEA turns the vibrations into electrical signals which get sent to your brain and allow you to sense the sound.

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28
Q

What range can humans hear sound at?

A

20Hz - 20kHz

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29
Q

Can microphones pick up sound outside of the humans range?

A

Yes, but if you tried to listen to the sound, you probably wouldn’t hear anything

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30
Q

How is the human hearing limited?

A

By the size and shape of our ear drum, as well as the structure of all the parts within the ear that vibrate to transfer the energy from the sound wave.

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31
Q

Can sound waves reflect and refract?

A

Yes, sound waves will be reflected by hard flat surfsces. Echoes are reflected sound waves.

Sound waves will also refract as they enter different media.
As they enter denser material, they speed up because when a wave travels into a different medium.
wavelenght changes but
its freuqnecy remains the same
so its speed must change.

32
Q

Fact File EM Waves:
Type of wave:
Speed:
What do Electromagnetic waves form:
Why is there a large range of frequencies:

A

TYPE OF WAVE: They are all transverse waves that transfer energy from a source to an absorber
SPEED: They all have the same speed through air or a vacuum (space).
WHAT DO EM WAVES FORM: they form a continuous spectrum over a range of frequencies. They are grouoed into 7 basic types, based on wavelength and frequency.
WHY IS THERE A LARGE RANGE OF FREQUENCIES: because EM waves are generated by a variety of changes in atoms and their nuclei.
Different properties, mean different EM waves are used for different purposes.

33
Q

What happens if you study the path of waves through structures?

A

It means that you can clues to some of the properties of the structure of waves that you cannot see by eye.

34
Q

How are seismic waves formed?

A

When there’s an earthquake somewhere, it produces seismic waves which travel out through the earth. We detect these waves all over the surface of the planet using seisometers.

35
Q

What happens when seismic waves reach a boundary between different layers of material inside the earth?

A

Some waves will be absorbed and some will be refracted.
If they are refracted they change speed gradually, resulting in curved path. But when props change suddenly, wave speed changes abruptly, making a kink

36
Q

What are the two different types of seismic waves?

A

P-waves and S-waves

37
Q

What is a P-wave and what is its properties?

A

P-waves are longitudinal, they travel through solids and liquids. They travel faster than S-waves

38
Q

What is a S-wave and what are its properties?

A

They are transverse waves and can’t travel through liqiuds (or gases). They are slower than P-waves

39
Q

What is ultrasound?

A

Sound waves above the highest frequency that humans can detect are called ultrasound waves.

40
Q

What is partial reflection?

A

When a wave passes from one medium into another, some wave is reflected off the boundary between the two media, and some is transmitted. This ia partial reflection. This is what also happens to ultrasound waves.

41
Q

The 3 uses of ultrasound

A

MEDICAL IMAGING: - ultrasound waves can pass through the body, whenever they reach a boundary between two different media some of the wave is relfected back and detected. - the exact timing and distribution of these echoes are processed by a computer to produce a video image of the feotus.

INDUSTRIAL IMAGING: ultrasound can be used to find flaws in objects such as pipes. - ultrasound waves entering a material usually reflect. If there is a crack in the object, it will reflect sooner.

ECHO SOUNDING- uses high frequency sound waves (ultrasound). It’s used by boats and subs to find the depth of water they are in.

42
Q

Experiment with waves: Use an oscilloscope to measure the speed of sound:

A

1) Set up the oscilloscope so the detected waves at each microphone are shown as separate waves.
2) start with both microphones next to the speaker, then slowly move one away until 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) find speed of sound waves passing through air.
5) 330m/s speed of sound in air, check results

43
Q

You can use the wave equation for waves on strings practical:

A

Take a picture of p74 CGP

44
Q

How are radio waves made?

A

You can produce radio waves using an alternating current in an electrical circuit. The onject in which charges oscillate to create the radio waves called a transmitter.
-when transmitted they reach the receiver, they are absorbed
- the energy carried by the waves is transferred to the electrons in the material of the receiver.
-causing electrons to oscillate, if the receiverid part of a complete circuit, it generstes an alternating current
- this has the same frequency as the radio wave thst generated it

45
Q

Describe the characteristics of long wave radio waves?

A

They can diffract (bend) around the curved surface of the earth. And can diffractaround hills, into tunnels e.t.c.
(Making it possible for radio signals to be recieved even if the reciever isnt in the line of the sight of the transmitter)

46
Q

Describe the characteristics of short-wave radio signals

A

-Can be recieved over long distances (like long wave radio signals) from the transmitter
- thats because they are reflectsd from the ionosphere - an electrically charged layer in earth’s upper atsmosphere.

See diagram on page 78 CGP

47
Q

What type of radio waves do TV and FM radio use?

A

They have very short radio wavelengths. To get reception, you must be in direct sight of the transmitter -the signal doesn’t have to bend or travel far theough buildings

48
Q

How are microwaves used by satellites.

A

1) the signal from a transmitter is transmitted into space
2) where it’s picked up by the satellite reciever dish in space.
3) the satelite transmits the signal back to earth in a different direction
4) where it is recieved by a satellite dish on the ground.

49
Q

How do microwave ovens use microwaves?

A

The microwaves penetrate up to a few centimetres into the food where they are being absorbed and transfer the energy they hold into the water molecules in the food and it heats up.
The water molecules transfer the energy to the rest of the molecules to heat up.

50
Q

Where is Infrared radiation found?

A

It is given out by all objects- the hotter an object is. The more it will give of IR.

51
Q

How do infrared cameras work?

A

They are used to monitor temperatures. The camera detects IR radiation and turns it into an electrical signal, which is displayed on a screen as a pic.

52
Q

What will absorbing IR radiation do?

A

It will mean that whatever it is being absorbed by will get hotter. You cancook food with IR radiation which will cause the food to heat up

53
Q

How do electric heaters work?

A

They contain a long piece of wire that heats up when a current flows through it.
This emits IR radiation. This is absorbed by objects and the air in the room.
Energy is transferred by IR waves to the thermal energy store of the objects, causing a temp increase.

54
Q

How can optical fibres be used to transmit data?

A

They are thin glass or plastic fibres that can carry data over long distances as pulses of visible light.
They work because of reflection.
Light rays are bounded back and forth until they reach the end of the fibre.
Light is not easily absorbed or scattered as it travels along a fibre

55
Q

What are the characteristics of fluorescent lights?

A

-They generate UV radiation, which is absorbed and re-emitted as visible light by a layer of a compound called a phosphor on the inside of the bulb.
-They are energy-efficient so they’re good to use when light is needed for long periods of time.

56
Q

How do security pens work?

A

They can be used to mark property with yournname. Under UV light the inj will glow (fluoresce), but its invisibke otherwise. This helps police identify property if its stolen

57
Q

UV radiation and how that affects tanning salons

A

UV radiaition is produced by the sun, and exposure to it gives people a suntan. However, if its not sunny, people go to tanning salons, too much exposure to UV radiation can be dangerous (fluorescent lights emit very little UV- totally safe.)

58
Q

How do X-rays work?

A

X-rays pass through flesh easily but not so easily through denser material like nones or metal. So it’s the amount of radiation absorbed that gives you the X-ray image.

59
Q

What are the uses of X-rays and Gamma rays?

A

X-rays and gamma rays are used to treat people with cancer (radiotherapy). This is because of the high doses of these rays kill all living cells- they are carefully directed st the cancerous cells to avoid killing healthy cells.

Gamma radiation ised for medical tracer - this is where gamma-emitting source is injected into the patient, and its progress is followed around the body. Its well suited to this because it can pass out through the body to be detected

60
Q

Can EM radiation be harmful to people?

A

When EM radiation enters living tissue - its often harmless, but sometimes it creates havoc. The effects of each type of radiation are based on how much energy the wave transfers.

61
Q

Whats the difference between low frequency waves and high frequency waves in terms of damage to living tissue?

A

Low frequency waves, like radio waves, don’t transfer much energy so mostly pass through soft tissue without being absorbed. Howevee, High Frequency Waves liek UV,X-rays and gamma rays all transfer lots of energy so can cause lots of damage.

62
Q

How is UV radiation harmful to people?

A

It can damage sirface cells, which canclead to sunburn and cause skin to age prematurelly. Can cause erious effects like increased risk of skin cancer and blindness.

63
Q

How are X-rays and gamma rays harmfuk to people?

A

They are types of ionising radiation. They carry enough energy to knock electrins off of atoms. This can cause gene mutation or cell destruction and cancer

64
Q

What is radiation dose?

A

It is a measure of the risk of harm from the body being exposed to radiation.

It is not a measure of the total amount of radiation being absorbed.
The risk depends on the total amount of radiation absorbed and how harmful the type of radiation is.

65
Q

What is the radiation dose measured in?

A

Sievert

66
Q

Are different parts of the body more at risk from other parts to damage from radiation

A

Bottom of page 81 CGP pic

67
Q

Do all objects emit IR radiaiton

A

Yes all objects continually absorb it

68
Q

What happens when an object is hotter/cooler and at the same constant temp than its surroundings?

A

It emits more IR radiation than it absorbs as it cools down.

And if an object is cooler than its surroundings it absorbs more IR radiation than it emits as it warms up.

If its at the same constant temp then it emits at the same rate as it absorbs it.

69
Q

Leslie cube practical. Pic inserted

A

1)Place an empty Leslie cube on a heat-proof mat.
2) Boil water in a kettle and fill the Leslie cube with boiling water.
3)Wait a while for cube to warm up, then hold a thermometer against each of
the four vertical faces of cube. You should find that all your faces are same temperature.

4) Hold infrared detector a set distance (e.g. 10 cm) away from one of the cube’s vertical faces, and record the amount of IR radiation it detects.

5) Repeat this measurement for each of the cube’s vertical faces. Make sure you position the detector at the same distance from the cube each time.

6) You should find that you detect more infrared radiation from the black surface than the white one, and more from the matt surfaces than the shiny ones.

7) As always, you should do the experiment more than once, to make sure your results are repeatable.
8) be careful when you’re doing experiment. Don’t try to move the cube when it’s full of boiling water might burn hands. Be careful if you’re carrying a full kettle.

70
Q

What is a perfect black body?

A

It is an object thst absorbs all of the radiation that hits it. No radiation is reflected or transmitted. They are the best possible emmitters of radiation

71
Q

What is intensity?

A

It is the power per unit area i.e how much energy is transferred to a given area in a certain amount of time.

72
Q

What happens when the temperature of an object increases in relation to intensity. And would the intensity increase or decrease depending on wavelength?

A

The intensity of every emmited wavelength increases.

However, the intensity increases quicker for shorter wavelengths than longer ones. Causing the peak wavelength (highest intensity) to decrease.

73
Q

How does the temp of the earth change in terms of radiation? In the day and in the night

A

It all depends on how much radiation is absorbed, reflected and emitted. In the day, more radiation is transferred to earth from sun and absorbed causing increase in temp. However, at night less radiation absorbed than being emitted, causing decrease in temp.

74
Q

What if the atmosphere changes in relation to temp?

A

Changes to the atmosphere can cause a overall change in temp. If the atmos starts to absorb more radiation without emitting the same amount, the overall temp will rise until absorption and emission are equal again

75
Q

If the wave is travelling into a less dense material, it will bend

A

Away from the normal

76
Q

If the wave is travelling into a more dense material it will bend

A

Toward the normal

Physics GCSE (15 decks)

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