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Physics GCSE > Waves > Flashcards

Waves Flashcards

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1
Q

What is the main purpose of waves?

A

They oscillate and transfer energy and information in the direction they are travelling.

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2
Q

What is a mechanical wave?

A

Mechanical wave is a wave that transfers energy through a medium.

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3
Q

What waves travel through a vacuum?

A

Waves that travel through a vacuum are known as EM waves and they do not require a medium.

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4
Q

What are longitudinal waves?

A

Oscillations are parallel to the direction of energy transfer. They move side to side and have compression and rarefractions.

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5
Q

What are transverse waves?

A

Waves propagate perpendicular to the direction of energy. They move up and do and have peaks and troughs

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6
Q

Give 3 examples of transverse waves?

A

electromagnetic radiation (1)
surface of water/water waves/in ripple tank (1)
rope (1)
slinky clearly qualified as transverse (1)
secondary (‘s’) waves (1)

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7
Q

Give examples of longitudinal waves

A

Sound waves, shock waves

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8
Q

What is the amplitude of a wave?

A

The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.

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9
Q

What is the wavelength of a wave?

A

The distance from a point on one wave to the equivalent point on the adjacent wave

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10
Q

What is the frequency of a wave?

A

The number of complete waves passing a certain point per second

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11
Q

What is the period of a wave?

Equation for period?

A

The period is the amount of time required for one complete cycle or oscillation.

T(s)= 1/f

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12
Q

how to calculate wave speed

A

wave speed = frequency x wavelength

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13
Q

What is the relationship with frequency and wavelength?

A

frequency is inver prop to wl

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14
Q

What are the three things that can happen when a wave arrives at a boundary?

A

1) Absorbed by the material the wave is trying to cross into which transfers energy to material’s energy stores
2) Is transmitted where it carries on travelling into the new material and often leads to refraction.
3) reflected

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15
Q

Whats the rule for reflection?

A

angle of incidence= angle of reflection.

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16
Q

What is refraction?

A

The waves change direction when they cross a boundary between 2 different mediums. The wave changes speed and direction therefore it’ll have the same frequency but different wavelength.

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17
Q

What are the two types of reflection and explain?

A

Specular reflection- happens when a wave is reflected in a single direction by a smooth surface eg- when light is reflected by a mirror.
Diffuse reflection- when a wave is reflected on a rough surface and the reflected rays are scattered in lots of different directions. This happens because the norm is diff for the incoming ray and thus the reflected ray is different.

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18
Q

Refractive index equation

A

sin i/sin r

Sin i - the angle of incidence
Sin r - the angle of refraction

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19
Q

How to calculate the refractive index using critical angle?

A

n(refractive index)= 1/sinC(Critical angle)

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20
Q

When does total internal reflection occur?

A

.When the incident ray is returning back to its original medium- it is known as total internal reflection.

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21
Q

What happens when a ray goes from more dense to a less dense and vice versa? What happens to the angle of refraction?

A

Less dense to more dense- ray will slow down and move towards the normal- angle of refraction is smaller than the angle of incidence
More dense to less dense- ray will speed up and move away from the normal- angle of refraction will be greater than angle of incidence.

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22
Q

What are sound waves caused by?

A

vibrating objects and the vibrations of air are passed through rarefactions and compressions.

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23
Q

What medium do sound waves travel faster in?

A

Solids- because all the molecules are more close together and as they have strong bonds, they are in a lattice hence less time will take for sound to pass to each other and the faster the sound can travel as sound will cause the particles to vibrate

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24
Q

Can sound waves travel through a vacuum?

A

No, because they require particles to move and vibrate.

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25
Q

What are reflected sound waves known as?

A

Echoes and they will be reflected by smooth hard surfaces.

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26
Q

What does the frequency and the amplitude of a sound wave determine?

A

Frequency determines the pitch and amplitude determines the loudness.

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27
Q

Range human ear can detect?

A

20Hz-20kHz

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28
Q

Process of sound reaching the ear?

A

1) Sound waves that reach your eardrum can cause it to vibrate
2) These vibrations are passed on to tiny bones in your ear called cochlea
3) The cochlea turns these vibrations into electrical signals which get sent to your brain via the auditory nerve & allow you to sense the sound

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29
Q

Evidence To prove wave moves and not the water itself?
-sound waves in air air itself that travels.
§

A

§§§Place an object on the surface of water- plastic duck and it will only bob in place up and down if the water does not move.

-Sound waves: A vibrating drum skin does not move the air away to create a vacuum (around the drum)

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30
Q

What are Ultra- sound waves?

A

Ultrasound waves are waves that are above the highest frequency the human ear can detect.

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31
Q

How can ultrasound be used in medicine ?

A

1) Prenatal scans of baby in the womb.

2) Used to get images of the organs in the body.

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32
Q

What is an ultrasound scanner made up of?

A

An electronic device called a transducer which produces and detects sets( or pulses) of US waves.

33
Q

How do US waves get partially reflected?

A

-Partially refracted at boundaries between the two media and some are reflected back and the time it takes for the reflection to reach the transducer can be measured how far away the boundary is.

34
Q

Advantages of ultrasound (3)

A
  • non-ionizing so they’re safer, especially for unborn babies
  • as they can be used to detect boundaries between different types of body tissue,
  • they give a better resolution than x-rays (which just show bone/not bone).
35
Q

Describe Pre-natal scanning?

A

US waves arrive at two different media( the baby and the womb) the waves will reflect back and be detected and the timing and the distribution of these echoes will be processed to produce a video image of the foetus.

36
Q

How can US scanners be used for industrial?

A

Flaws in metal cracks can be detected using US waves and a flaw may be an internal crack which creates a boundary inside the metal and the US waves will partly reflect from the boundary and the internal crack can cause the waves to reflect back sooner.

37
Q

Purpose of oscilliscope

A

Be used to measure the time taken by the wave from transmitter and to and fro from the boundary that is reflected on.

38
Q

List 3 other uses of US waves?

A

Removing Dental Plaque, breaking up kidney stones, treating injuries.

39
Q

How is a seismic wave created?
How do we detect these waves?
Purpose?

A

Seismic waves are created when an earthquake or an explosion occurs and the energy transferred makes shock waves called seismic waves to travel through the earth and its surface. We detect them using seismometers.

They help provide info about the structure of the earth. This is beacuse by observing how seisimic waves are absorbed and refracted, scientists have able to work out where the properties of the Earth change dramatically - helps us understand the internal structure of the Earth and the size of the Earth core.

40
Q

Two types of seismic waves. Describe their feature.

What do seismis waves do when they reach a boundary?

A

P waves and S waves.

  • P Waves(primary waves) are longitudinal waves and can travel through liquids and solids and are faster than S waves.
  • S waves( secondary waves) are transverse waves that can travel through solids.

When seismic waves reach a boundary between different layers of material inside the Earth, some of the waves will be absorbed and some with be refracted. Most of the time, if the waves are refracted, they change speed gradually resulting in a curved path but when the properties change suddenly, the wave speed changes abruptly and the path has a kink

41
Q

What do EM waves transfer? What type are they?

A

They transfer energy from a source to an absorber. They’re transverse waves and all travel at the speef of light( 3x10^8m/s) in a vacuum.

42
Q

Lowest energy to highest energy in EM?

A

RMIVUXG- Radio Waves have lowest energy, longest wl and lowest frequency whereas GR have the highest energy, the shortes wl and the highest freq.

43
Q

Uses for radio waves, microwaves, infrared and visible light?.

A

RW- satellite, mobile phones, TV broadcasting- they can spread out so the signal doesn’t weaken.
MW- cooking, mobile phones.
Infra re- optical fibres, communication, electric heaters, heating food up, detecting forged bank notes.
Visible light- light, optical fibres

44
Q

Uses of X-rays

A

Xrays can be used to detect internal flaws/cracks in metals( the more dense an object is, the more Xray it absorbs)
-Used in medicine to create images of broken limbs- it cannot pentrate through tissue.

45
Q

Dangers of x-rays and gamma rays

A

Cause mutations to DNA in body cells- Ionising. High doses kill cells while low doses cause skin cancer. Can cause blindness to the eyes.

46
Q

How are Gamma rays different to Xrays?

What does the effect of the radiation depend?

A

As both X-rays and gamma rays have very short wavelengths they are both very penetrating and can pass into the body to treat internal organs.

The main difference between them is the way they’re produced. X-rays are produced by firing electrons at a metal target in an X-ray machine. Gamma rays are emitted by the nucleus of an unstable (radioactive) atom.

The effects depend on the type of radiation and the size of the dose. Radiation dose (in sieverts) is a measure of the risk of harm resulting from an exposure of the body to the radiation.

47
Q

Uses of gamma rays?

A

killing bacteria, killing cancer cells.

- sterilising surgical equipment

48
Q

How are Gamma rays and Xrays similar?

A
  • They are at the short wl end of the electromagnetic spectrum.
  • Carry more energy per second than longer wl electromagnetic waves.
49
Q

Convex lens and concave lens shape and purpose?

A
  • Convex lens a lens that is thicker in the middle than at the edges and is a converging lens that causes the light rays to converge and meet at a certain point.
  • Concave lens in a diverging lens and it is thinner in the middle as it caves in and it causes the light rates to diverge and spread out.
50
Q

What can convex/converging lenses be used for?(3)

What can a concave lens be used for?(1)

A

glasses for long-sighted people

  • magnifying glass
  • and in a camera to form a clear image of a distant object.
  • > Concave can be used for treating short sighted people.
51
Q

What is the focal length?

A

The distance from the centre of the lens to the principal focus

52
Q

What type of image does a converging(convex) lens produce?

A

1) Real, diminished and inverted when the object is at a further distance away from the principal focus.
2) and virtual when the image is closer to the principal focus-it’ll form an inverted, magnified and virtual image.

53
Q

What type of image does a diverging(concave) lens produce?

A
  • always virtual, upright, diminished.
54
Q

What type of lens does a camera contain and what does it produce?
What does a magnifying glass contain and what does it produce?

A
  • Both contain convex lens however camera uses the convex lens to produce a real image.
  • Magnifying glass use convex to produce a virtual image.
55
Q

What happens when an object is placed between the convex lens and the principle focus(F)?

A

The image formed is virtual, upright and magnified and on the same side of the lens of the object.

56
Q

Magnification equation?

A

Image size/actual size

57
Q

If light travels slower in glass, what does it say?

A

glass is more optically denser than air.

58
Q

How do colour filters work?

What would happen if there is a blue filter but the object was red?

A

They only let through particular wavelengths.
Colour filters work by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour).

-The object would appear black when viewed through a blue filter as all of the light reflected by the object will be absorbed by the filter

59
Q

What do white objects? What do black objects do?

A

White objects reflect all of the wl of visible light equally. Black objects absorb all wavelengths of visible light.

60
Q

What does a translucent object do?

A

Translucent objects lets all light pass through it BUT scatters or refracts the light inside it. This is because the material has lots of internal boundaries that change the direction of the light repeatedly.

61
Q

What does a transparent object do?

A

All the light that enters it pass through it and does not scatter or refract the light inside it. No light is absorbed.

62
Q

What does an opaque object do?

What does the colour of an opaque object depend on?

A

-Do not transmit light. We can only see the surface because the light waves are re-emitted from the surface back to our eyes. Opacity occurs because of the reflection of light waves off the surface of an object.
When VL hits them, they absorb some of the wavelengths of light and reflect them.

-It depends on the pigments of colour on the surface and what wavelengths of light the pigments absorb and which they strongly reflect.

63
Q

What is a perfect black body?

What wave do all objects emit and why?

What does the intensity and the distribution of the EM waves depend on?

A
  • an object that absorbs all of the radiation that hits it and no radiation is reflected or transmitted.-Perfect black bodies are the best possible emittors of radiation.
  • All objects emit EM wave due to the energy in their thermal energy stores. The radiation covers a range of wavelengths and frequencies.
  • Intensity and distribution of the wavelengths emitted by an object depend on the object’s temperature. As the temp of an object increases, the intensity of every emitted wl increases, however, the intensity increases more rapidly for shorter wl than longer wl and this causes the wl with the highest intensity to decrease.
64
Q

What is a body at constant temperature?

A

body at constant temperature is absorbing radiation at the same rate as it is emitting radiation. The temperature of a body increases when the body absorbs radiation faster than it emits radiation.

65
Q

There are 3 factors that the Earth’s surface depends on; what are the three factors?

A

The temperature of the Earth depends on many factors including: the rates of absorption and emission of radiation,emission of radiation into space.

66
Q

Equation for magnification and why does it not have any units?

A

The magni cation produced by a lens can be calculated using the equation:
magni cation = image height/ object height
Magni cation is a ratio and so has no units.

67
Q

How does a convex lens represented differently to a conave lens?

A

In ray diagrams a convex lens will be represented by:
A concave lens will be represented by:
>——<

Convex:

68
Q

How are EM waves produced?

A

-They are produced by oscillating electrical and magnetic fields. AC is made up of oscillating charges and as the charges oscillate, they produce oscillating electric and magnetic fields, i.e electromagnetic waves. The frequency of the waves will be equal to the frequency of the AC.

69
Q

Where do gamma rays originate from?

A

Gamma rays originate from changes in the nucleus of an atom.

70
Q

What is echo sounding?

A

Echo sounding, using high frequency sound waves is used to detect objects in deep water and measure water depth.

71
Q

How is the Earth’s local temp determined?

A

-During the day, lots of radiation is absorbed from the Sun and causes an increase in local temp but during the night, less radiation is being absorbed than is being emitted, causing a decrease in local temp which allows the temp of the Earth to stay fairly constant.

72
Q

What happens to the radiation when it hits Earth surface?(3)

A

1) some radiation is absorbed by the atmosphere, clouds and the Earth’s surface.
2) Some radiation is reflected by the atmosphere, clouds and the Earth’s surface.
3) radiation is also emitted.

73
Q

What are all objects continually doing in regards to IR radiation?

What happens if the temp increase/decrease of an object?

What surfaces are better emitters?
What surfaces are better absobers?

A
  • continually emitting and absorbing IR radiation and IR is emitted from the surface of an object.
  • the hotter an object is from its surround, the more IR radiation it emits into surroundings than it absorbs as it cools down. An object that is cooler than its surrounded absorbs more IR radiation than it emits as it warms up
  • white surface and a Dull, matt or rough surface is better at absorbing and emitting radiation than a shiny one.
  • black surfaces are the best absorbers of radiation and the best emittors.
74
Q

How can radio waves be produced?

A

Radio waves can be produced by oscillations in electrical circuits by a transmitter.
When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical circuit.

75
Q

What are radio waves mainly used for?

How can short wave radio be used?

What radio waves do TV and FM radio emission use?

A
  • Mainly used for communication.
  • Longwave radio can diffract around hills and can bend around the Earth and makes it possible for radio signals to be received even if the receiver isn’t in the line of the sight o the transmitter.
  • Short wave radio signals can be recieved at long distances from the transmitter and that’s because they are reflected from the ionosphere- an electrically charged layer in the Earth’s upper atmosphere- Bluetooth uses short wave radio waves (wireless headphones)
  • Radio waves used for TV and FM radio emission have v short wl and to get reception, you must be in direct sight of the transmitter as the signal doesn’t bend or travel far through builds.
76
Q

How do microwaves warm up food?

A

-in microwave ovens, microwaves need to be absorbed by water molecules in food and the microwaves penetrate up to a few cm into the food before being absorbed and transferring the energy they are carrying to the water molec in food, causing the water to heat up. The water molecules then transfer this energy to the rest of the molecules in the food by heating- which quickly cooks the food.

77
Q

Purposes for visible light?

A

-optical fibres are thin glass or plastic fibres that can carry data over long distances as pulses of visible light; they work because of reflection and the light rays are bounced back and forth until they reach the end of the fibre.

78
Q

What is the difference between real and virtual images?

A

virtual image cannot be projected on to a screen and the rays of light are imaginary whereas a real image can be projected on a screen because it is formed by focusing light rays on to the screen.

Physics GCSE (8 decks)

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