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Physics Paper 2 > Waves > Flashcards

Waves Flashcards

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1
Q

what is a transverse wave?

A

The oscillations are perpendicular to the direction of energy transfer.
A spring wiggled side to side gives a transverse wave

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2
Q

What is a longitudinal wave?

A

The oscillations are parallel to the direction of energy transfer.
If you push the end of a spring, you get a longitudinal wave.

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3
Q

Examples of transverse waves?

A

-all electromagnetic waves
-ripples and waves in water
- wave on a string
{most waves}

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4
Q

Examples of longitudinal waves?

A
  • sound waves in air, ultrasound

- shock waves, seismic waves

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5
Q

How do you calculate the wave speed?

A

Wave speed (m/s) = frequency (Hz) X wavelength (m)

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6
Q

What is the frequency of a wave?

A

The number of complete waves passing a certain point per second. Measured in hertz (Hz)

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7
Q

What is the amplitude of a wave?

A

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

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8
Q

What is the wavelength?

A

The distance between the same point on two adjacent waves

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9
Q

How do you calculate the period of a wave?

A

The amount of time it takes for a full cycle of waves to pass a point

Period = 1/ frequency

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10
Q

What is the angle of incidence?

A

Angle of incidence = angle of reflection

-the angle between the incoming wave and the normal

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11
Q

What is specular reflection?

A

When a wave is reflected in a single direction by a smooth surface (eg when lit is reflected by a mirror you get a clear reflection)

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12
Q

What is diffuse reflection?

A

When a wave is reflected by a rough surface (eg paper) and the reflected rays are scattered in many different directions

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13
Q

What is refraction?

A

When a wave crosses a boundary between materials at an angle, it changes direction and so it is refracted

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14
Q

What is the frequency of a wave?

A

The number of complete waves passing a certain point per second. Measured in hertz (Hz)

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15
Q

What is the amplitude of a wave?

A

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

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16
Q

What is the wavelength?

A

The distance between the same point on two adjacent waves

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17
Q

How do you calculate the period of a wave?

A

The amount of time it takes for a full cycle of waves to pass a point

Period = 1/ frequency

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18
Q

What is the angle of incidence?

A

Angle of incidence = angle of reflection

-the angle between the incoming wave and the normal

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19
Q

What is specular reflection?

A

When a wave is reflected in a single direction by a smooth surface (eg when lit is reflected by a mirror you get a clear reflection)

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20
Q

What is diffuse reflection?

A

When a wave is reflected by a rough surface (eg paper) and the reflected rays are scattered in many different directions

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21
Q

What is refraction?

A

When a wave crosses a boundary between materials at an angle, it changes direction and so it is refracted

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22
Q

Which rule applies to all reflections?

A

Angle of incidence = angle of reflection

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23
Q

What is an experiment you could do to investigate refraction?

A
  • place rectangular transparent block on a piece of paper and trace around it
  • use a ray box or laser to shine a ray of light at the middle of one side of block
  • trace the incident Ray and mark where light Ray emerges on the other side of block
  • remove block and join up incident Ray and emerging point to show the refracted Ray brought the block
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24
Q

Why must you do light experiments in a dim room?

A
  • so you can clearly see the paths of the rays of light

- Ray box and laser means more accurate angle measurements as Ray’s can be traced more accurately

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25
Q

What is an experiment to investigate reflection and light?

A
  • take piece of paper and draw a straight line across it. Place an object on the line
  • shine a ray of light at the objects surface and trace the incoming and reflected light beams
  • draw the normal at the point where the Ray hits the object
  • use protractor to measure angle of incidence and angle of reflection
  • repeat for a range of objects
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26
Q

What is an electromagnetic wave?

A
  • transverse waves that transfer energy from a source to an absorber
  • they all travel at same speed through air or a vacuum (space)
  • they form a continuous spectrum over a wide range of frequencies
  • grouped into seven basic types depending on their wavelength and frequency
27
Q

How are radio waves created?

A
  • using an alternating current in an electrical circuit

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

28
Q

What are uses of EM waves?

A

Long radio waves- can be transmitted from around the world even if the receiver isn’t in sight of the transmitter

Short wave radio waves-can be received at long distances from the transmitter

Bluetooth-uses short wave radio waves
TV/radio- very short wavelengths and you must be in sight of transmitter

29
Q

What is infrared radiation?

A

Given out by all objects and the hotter the object, the more IR radiation it gives out

30
Q

What do infrared cameras do?

A
  • used to detect infrared radiation and monitor temperature
  • it detects IR radiation and turns it into an electrical signal which is displayed as a picture on a screen
  • the hotter an object is, the brighter it appears
31
Q

What is an optical fibre?

A

Thin glass or plastic fibres that carry data over long distances as pulses of visible light

  • work because of reflection
  • light is not easily absorbed or scattered as it travels along a fibre
32
Q

What is ultraviolet radiation?

A

Produced by the son and exposure to it is what gives people a sun tan.
-present in sun beds in UV lamps to give artificial tan > overexposure can be dangerous

33
Q

What is the purpose of X Ray’s?

A
  • To identify any broken bones in the body

- can treat people with cancers (radiotherapy)

34
Q

How do X rays work?

A

It is the amount of radiation that is absorbed that gives you an X Ray image
-the brightest bits are where fewer X Ray’s get through so they aren’t as accurate as the darker parts

35
Q

How are X Ray’s and gamma rays used in radiotherapy?

A

-high doses of these Ray’s kills all living cells so they are directed to kill the cancer cells in a specific area

36
Q

What are the dangers of X rays and gamma rays?

A
  • types of ionising radiation which can causes gene mutation or cell destruction and cancer
  • radiographer swear lead aprons and stand behind a lead screen because it doesn’t emit this radiation
37
Q

How are TV signals transmitted from a transmitter on the ground to a house?

A
  • transmitted through atmosphere into space
  • picked up by satellite receiver orbiting Earth
  • satellite transmits signal back to Earth in a different direction
  • then received by a satellite dish connected to the house
38
Q

How do lenses form images?

A

They refract light and change its direction

39
Q

What is a convex lens?

A
  • bulges outwards

- causes rays of light parallel to the axis to be brought together at the principal focus

40
Q

What is a concave lens?

A
  • caves inwards
  • causes rays of light parallel to axis to spread out (diverge)
  • ALWAYS produces a virtual image that is upright and smaller than the object
41
Q

What is a real image?

A

Where the light from an object comes together to form an image on a screen

42
Q

What is a virtual image?

A

When the rays are spreading out so the light from the object appears to be coming from a completely different place
Eg your face in a mirror and looking through a magnifying glass

43
Q

How do you describe an image properly?

A
  • how big it is compared to object
  • whether it’s upright or inverted (upside down)
  • whether it’s real or virtual
44
Q

How do you calculate the magnification?

A

Magnification = image height / object height

45
Q

What are opaque objects?

A

They do not transmit light. When visible waves hit them, they absorb some wavelengths of light and reflect others

46
Q

What are transparent/translucent objects?

A

They transmit light. Not all light that hits the surface of the object is absorbed or reflected-some can pass through

47
Q

What are colour filters used for?

A

To filter out different wavelengths of light so that only certain colours are transmitted, the rest are absorbed
Eg red cellophane (red or black)-transparent object

48
Q

What is a perfect black body?

A

An object that absorbs all of the radiation that hits it. No radiation is reflected or transmitted
-the best possible emitters of radiation

49
Q

What does the temperature of the earth depend on?

A

The amount of IR radiation it reflects, absorbs and emits

50
Q

Why does the temperature of the earth stay fairly constant?

A
  • during day lots of radiation (light) is transferred to Earth from sun and is absorbed-increase in local temp
  • at night less radiation is being absorbed than it is being emitted-decrease in local temp
  • overall temp of earth stays fairly constant
51
Q

What causes a sound wave?

A
  • vibrating objects.

- vibrations passed through the surrounding medium as a series of compressions and rarefactions

52
Q

Why does a sound wave travel best in a solid and not in a gas, liquid or space?

A
  • when a sound travels through a solid, it causes the particles to vibrate
  • sound can’t travel in space because it’s a vacuum (no particles to vibrate)
53
Q

How do sound waves travel to the ear?

A
  • vibrations passed to ossicles in ear, through semicircular canals and to the cochlea.
  • cochlea turns thee vibrations into electrical signals which are sent to the brain and so we hear the sound
54
Q

What range of sound can humans hear? What affects this?

A

20Hz-20kHz

-hearing is limited by size and shape of our ear drum

55
Q

What are echoes? How are they caused?

A
  • sound waves are reflected by hard flat surfaces

- echoes are just reflected sound waves

56
Q

What is an ultra sound?

A
  • electrical device which produce electrical oscillations of any frequency
  • converted into mechanical vibrations to produce sound waves beyond range of human hearing
57
Q

How do microphones work?

A

Sound waves cause diaphragm to vibrate and this movement is transferred into an electrical signal

58
Q

How are ultrasounds used in the medical industry?

A
  • ultrasound waves can pass through body
  • when they reach boundary between two different media (eg fluid and skin of foetus) some of the wave is reflected back and detected
  • the exact timing and distribution of these echoes are processed by a computer to produce a video image of foetus (scan)
59
Q

What happens when there is an earth quake?

A

Seismic waves are created and travel through the earth. They are detected by seismometers

60
Q

What happens when seismic waves reach a boundary?

A

When they reach a boundary between different layers of material inside the earth, some waves will be absorbed and some will be refracted

61
Q

What usually happens if waves are refracted?

A

They change speed gradually, resulting in a curved path. But if properties change suddenly, the wave speed changes abruptly and the path has a kink

62
Q

What are P-waves?

A

-longitudinal
-travel through solids and liquids
-travel faster than S-waves
(Seismic wave)

63
Q

What are S-waves?

A

-transverse
-can’t travel through liquids or gases
-slower than P-waves
(Seismic wave)

Physics Paper 2 (4 decks)

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