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PHYSICS > WAVES > Flashcards

WAVES Flashcards

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1
Q

What do waves do?

A

Transfer energy from one place to another without transferring any matter

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2
Q

What happens when waves travel through a medium?

A

The particles of the medium oscillate (vibrate) and transfer energy between each other

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3
Q

What is the amplitude of a wave?

A

The maximum displacement of a point on a wave from his undisturbed position

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4
Q

What is the wavelength of a wave?

A

The distance between the same point on two adjacent waves

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5
Q

What is the frequency of a wave?

A

The number of complete waves passing a certain point per second

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6
Q

What are transverse waves?

A

Vibrations go up and down (perpendicular to the direction of energy transfer)

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7
Q

What are examples of transverse waves?

A

All electromagnetic waves
Ripples and waves in water

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8
Q

What are examples of longitudinal waves?

A

Sound waves
Shock waves

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9
Q

What are longitudinal waves?

A

The vibrations are in the same direction the wave travels (side to side)

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10
Q

What is wave speed?

A

The speed at which energy is being transferred

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11
Q

What can happen when a wave arrives at a boundary?

A

Absorbed by material and energy is transferred to that energy store
The waves carry on travelling through the new material (refraction)
They are reflected

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12
Q

What is the angle of incidence?

A

The angle between the incoming wave and the normal

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13
Q

What is the angle of relfection?

A

The angle between the reflected wave and the normal

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14
Q

What is the angle of incidence equal to?

A

The angle of reflection

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15
Q

What is specular reflection?

A

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

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16
Q

What is diffuse reflection?

A

When a wave is reflected by a rough surface

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17
Q

Why does diffuse reflection happen?

A

Because the normal is different for each incoming ray

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18
Q

What is the order of electromagnetic waves?

A

Radio waves
Micro waves
Infra red
Visible light
Ultra violet
X-rays
Gamma rays

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19
Q

What are electromagnetic waves?

A

Transverse waves that transfer energy from a source to an absorber

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20
Q

What is refraction?

A

When a wave crosses a boundary between materials at an angle and it changes direction

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21
Q

How does the speed of a wave affect its refraction?

A

If it slows down when it crosses the boundary it will bend towards the normal
If it speeds up as it crosses the boundary it will bend away from the normal

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22
Q

What is the optical density of an object?

A

The measure of how quickly light can travel through an object

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23
Q

What are radio waves used for?

A

Communication such as broadcasting TV and radio, communications and satellite transmissions

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24
Q

What do long radio wave signals do?

A

Bend around the earth because their long wave lengths diffract around the curved surface of the earth

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25
Q

What do long radio wave signals do?

A

Bend around the earth because their long wave lengths diffract around the curved surface of the earth (long distances)

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26
Q

What do short radio wave signals do?

A

Reflect off the ionosphere (long distances)

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27
Q

What are microwaves used for?

A

Communication to and from satellites
Microwave oven

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28
Q

What happens in microwave ovens?

A

The microwaves are absorbed by water molecules in the food (they transfer their energy to the molecules causing the water to heat up)

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29
Q

What is infrared radiation?

A

This is given out by all hot objects

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30
Q

What can infrared radiation be used for?

A

Electric heaters
Cooking food

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31
Q

What can visible light be used for?

A

Optical fibres in fibre optic cables which carry data over long distances as pulses of visible light (light rays bounce back and forth)

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32
Q

What can ultraviolet be used for?

A

Security pens
Produced by sun to give people tans

33
Q

What can X-rays and gamma rays be used for?

A

X-ray photographs to see if any bones are broken
Treat cancer (kill cancer cells)

34
Q

How does UV radiation cause harm to humans?

A

Damages surface cells
Blindness
Increased risk of skin cancer

35
Q

How does gamma and x-rays cause harm to humans?

A

Ionising radiation so knock electrons off of atoms so can cause gene mutation or cell destruction and cancer

36
Q

How do lenses form images?

A

By refracting light and changing its direction

37
Q

What is the shape of a convex lens?

A

Bulges outwards

38
Q

What is the shape of a concave lens?

A

Caves inwards

39
Q

What is the axis of a lens?

A

A line passing through the middle

40
Q

What is the principle focus of a lense?

A

Where rays coming out from the lens meet (or align back to for concave lenses)

41
Q

What is the difference between a real and virtual image?

A

Virtual image is when both the image and the object are on the same side of the lens

42
Q

How do you describe an image?

A

Magnified or smaller
Real or virtual
Upright or inverted

43
Q

How do you draw a ray diagram for a convex lens?

A

From the top of the object draw:
a line going through the middle
a line parallel to axis then through the F

44
Q

How do you draw a ray diagram for a concave lens?

A

From the top of the object draw:
a line going through the middle
a line parallel to axis then through the F the same side as the object

45
Q

What images do concave lenses always make?

A

Virtual images
Upright
Smaller

46
Q

What happens during refraction?

A

A wave meets a new medium (like glass) and slows down then returns to its normal speed out the other side

47
Q

What do white objects do (light)?

A

Reflect all of the wavelengths of visible light

48
Q

What do black objects do (light)?

A

Absorb all of the wavelengths of visible light

49
Q

What are colour filters used for?

A

They are used to filter out different wave lengths of light so that only certain colours are transmitted and the rest are absorbed

50
Q

What happens when white light is shone at a blue colour filter?

A

Only blue light will be let through and the rest will be absorbed

51
Q

What would happen if a red hat was looked at through a blue filter?

A

The object would appear black as all of the light that is being reflected by the object will be absorbed by the filter

52
Q

What are EM waves made of?

A

Made up of oscillating electric and magnetic fields

53
Q

How are EM waves produced?

A

Alternating currents are made up of oscillating charges
As chargers ossification they produce oscillating electric and magnetic field

54
Q

How can you make radio waves using an alternating current in an electrical circuit?

A

Transmitter charges oscillate to create radio waves
Energy carried by waves using AC in current reach a receiver and transferred to electrons
Energy causes electrons to oscillate and create AC

55
Q

What are infrared cameras?

A

Detect infrared radiation and monitor temperature

56
Q

How does infrared cameras work?

A

Detects IR radiation and turns it into electrical signal which can be displayed as picture on screen

57
Q

What happens when an object absorbs infrared radiation?

A

It becomes hotter

58
Q

How do electric heaters work?

A

Long piece of wire which has a current flowing through it which emits infrared radiation
Energy is transferred to objects thermal energy stores when they absorb the IR radiation

59
Q

How do fluorescent lights work?

A

They absorb UV radiation and re emitt as visible light

60
Q

What is a perfect black body?

A

An object that absorbs all of the radiation that hits it (no radiation reflected or transmitted)

61
Q

What does the overall temp of the earth depend on?

A

The amount of radiation it reflects, absorbs and emits

62
Q

What are sound waves caused by?

A

Vibrating objects

63
Q

How do sound waves work?

A

Vibrating objects pass vibrations through surroundings medium as a series of compressions and rarefactions

64
Q

Through what medium does sound usually travel fastest in?

A

Solids

65
Q

Why can’t sound travel in space?

A

Because it is mostly a vacuum (no particles to move or vibrate)

66
Q

How do your ears receive sound waves?

A

Causes ear drum to vibrate
Vibrations pass on to tiny bones called ossicles to the cochlea
Vibrations turned into electrical signals which get sent to brain

67
Q

What is humans hearing sound range?

A

20Hz - 20kHz

68
Q

What can sound waves be reflected by?

A

Hard flat surfaces

69
Q

What can sound waves be reflected by?

A

Hard flat surfaces

70
Q

What are echoes?

A

Reflected sound waves

71
Q

Why do sound waves refract as they enter a different medium?

A

Enter denser material they speed up
Because wavelength changes but frequency remained the same so speeds up

72
Q

What is ultrasound?

A

Sound with frequencies higher than 20000Hz

73
Q

What is partial reflection of ultrasound?

A

Some passes from one medium to another and some of the wave is reflected off the boundary and some is transmitted

74
Q

How can ultrasounds be useful?

A

Medical imaging
Industrial imaging

75
Q

How can you use ultrasound to measure how far away a object is?

A

Point ultrasound at object
Some ultrasound gets reflected back at boundary
Time it takes for radiation to reach detector is how far away object is

76
Q

What are the two types of seismic waves?

A

P and S waves

77
Q

What are P waves?

A

Longitudinal
Travel through solids and liquids
Travel faster than S waves

78
Q

What are S waves?

A

Transverse
Cant travel through liquids or gases
Slower than P waves

PHYSICS (12 decks)

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