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physics - waves Flashcards

1
Q

What do waves do?

A

Transfer energy from one area to another with out transferring matter

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2
Q

What is the wavelength

A

The distance from one trough to another trough or peak to peak

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3
Q

What is the amplitude

A

The amplitude of a wave is the maximum displacement
from the equilibrium position (the x-axis).

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4
Q

What is the time period

A

The time period is the time it takes for one entire oscillation of the wave

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5
Q

Unit for frequency

A

Hz

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6
Q

What is a traverse wave

A

Oscillations are perpendicular to the direction of the energy transfer

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7
Q

What is a longitudinal wave

A

Oscillations are parallel to the direction of the energy transfer

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8
Q

Depending on conditions, when light hits a material it can be

A

Reflected, absorbed, transmitted

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9
Q

Where does specular reflection happen

A

Specular reflection occurs on surfaces where the boundary is flat

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10
Q

What type of image will specular reflection produce?

A

A clear image

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11
Q

Where does diffuse reflection occur

A

Diffuse reflection occurs on materials where the surface is bumpy

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12
Q

What is refraction

A

Refraction refers to changes in direction of the wave as it passes from one medium to another and it’s caused by it’s change in speed

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13
Q

Light travels more ____ in a more dense material

A

slowly

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14
Q

Light travelling from a less dense material to a more dense material will bend ____ the normal

A

towards

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15
Q

Light travelling from a more dense material to a less dense material will _____ the normal

A

away from

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16
Q

What happens to wave speed and frequency when a wave travels into a more dense medium

A

Wave speed - decreases
Frequency - Stays the same

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17
Q

What happens to wave speed and wave length when a wave travels into a more dense medium

A

Wave speed - decreases
Wave length - decreases

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18
Q

Are electromagnetic waves transverse of longitudinal

A

Transverse

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19
Q

What speed does electromagnetic waves travel at in a vacuum

A

3 x 10(8) m/s

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20
Q

What are true about radio waves

A

Have a long wavelength and low frequency

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21
Q

What are true of gamma rays

A

Have a short wavelength and high frequency

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22
Q

Which types of electromagnetic waves can be used in communication

A

Microwaves
Radio waves

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23
Q

Which of the following types of electromagnetic waves are considered ionising?

A

Gamma rays
X rays

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24
Q

How can you produce radio waves

A

Using an alternating current in an electrical circuit.

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25
Q

What are EM waves made up of

A

Electrical and magnetic fields

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26
Q

What are alternating currents made up of

A

Oscillating charges

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27
Q

How can you produce radio waves

A

Using an alternating current in an electrical circuit. The waves will be transmitted to the receiver and radio waves are absorbed.

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28
Q

What us a transmitter in terms of radio waves

A

The object in which charges oscillate to create the radio waves

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29
Q

What happens when the waves reach the receiver

A

The energy 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.

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30
Q

What are radio waves used for

A

Communication

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31
Q

How can long-wave radios be transmitted so far

A

They diffract around the curved surface of the Earth as well as hills and into tunnels. This makes it possible for radio signals to be receiver even if the receiver isn’t in line of the sight of the transmitter.

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32
Q

How can short-wave radio signals be transmitted so far

A

They are reflected from the inonosphere

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33
Q

What wavelengths do TV and FM radio use

A

Very short wavelengths. To get reception, you must be in direct sight of the transmitter.

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34
Q

What wave on the EM spectrum has the longest wave length and the lowest frequency

A

Radio waves

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35
Q

What are oscilloscopes used for

A

To display the frequency of an alternating current

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36
Q

What EM wave is used by satellites and why

A

Microwaves can pass easily through the Earth’s watery atmosphere

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37
Q

How does satellite TV work

A

The signal from a transmitter is transmitted into space where it’s picked up by the satellite receiver dish orbiting thousands of kilometres above the earth. The satellite transmits the signal back to Earth in a different direction where it’s received by a satellite dish on the ground.

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38
Q

What are microwaves used for

A

Microwave ovens and satellites

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39
Q

How do microwave ovens use microwaves

A

The microwaves are absorbed by water molecules in food. The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to thew water molecules in the 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

40
Q

What are some uses of infrared radiation

A

Infrared cameras can be used to detect infrared radiation and monitor temperature.
Cooking food - the temperature of the food increases when it absorbs IR radiation

41
Q

What are optical fibres

A

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

42
Q

How do optical fibres work

A

The light rays are bounced back and forth ubtil they reach the end of the fibre

43
Q

Uses of ultraviolet radiation

A

Passport security
Sun beds
Destroy microorganisms in water sterilisation.

44
Q

What does fluorescense mean

A

property of a chemical where UV radiation is absorbed and then visible light is emitted

45
Q

Uses of X-rays

A

X-rays are used to taker photographs of people to see if they have any broken bones
Can be used to treat people with caner

46
Q

How do X-rays work

A

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

47
Q

Uses of gamma radiation

A

Used as a medical tracer
Can be used to treat cancer

48
Q

How can gamma radiation and X-rays treat cancer

A

High doses of these rays kill all living cells - so they can be carefully directed towards cancer cells

49
Q

How do lenses form images

A

By refracting light and changing its direction

50
Q

Two main types of lenses

A

Concave and convex

51
Q

Shape of convex lens and what does it cause rays to do

A

Bulges outwards and causes rays of light parallel to the axis to be brought together (converge) at the principal focus

52
Q

Shape of concave lens and what does it cause rays to do

A

Caves inwards and causes rays of light to spread put (diverge) at the principal focus

53
Q

What are the three things that objects do with wavelengths

A

Absorb, transmit and reflect

54
Q

What are opaque objects

A

Objects that do not transmit light. When visible light waves hits them, they absorb some wavelengths of light and reflect others.

55
Q

What does the colour of an opaque object depend on

A

Depends on which wavelengths of light are most strongly reflected. The other wavelengths are absorbed

56
Q

What wavelengths do white objects reflect

A

White objects reflect all wavelengths of visible light equally.

57
Q

What wavelengths do black objects reflect

A

Black objects reflect no light and absorb all wavelengths of visible light.

58
Q

What do transparent and translucent objects do with light

A

They transmit light so not all light that hits the surface of the object is absorbed or reflected

59
Q

What is a primary colour filter

A

Only allows one of the three primary colours to be transmitted

60
Q

What are the primary colours

A

Red, green and blue

61
Q

A green glass bottle appears green because:

A

The bottle reflects and/or transmits green light and absorbs other colours of light.

62
Q

Objects that are hotter than their surroundings emit ____________ radiation than they absorb.

A

more

63
Q

An object at room temperature emits mostly

A

infrared radiation

64
Q

What happens to the land at night time

A

It absorbs more energy than it emits and its local temperature decreases

65
Q

How does sound travel

A

As a wave

66
Q

What are sound waves caused by

A

Caused by vibrating objects, these vibrations are passed through the surrounding medium as a series of compressions and rarefactions

67
Q

How does sound travel in different states of matter

A

Sound generally travels faster in solids than in liquids
Faster in liquids than in gases

68
Q

Why can’t sound travel in space

A

Because it’s mostly a vacuum so there are no particles to move or vibrate

69
Q

What happens when sound waves reach your ear

A

Your eardrum can vibrate. These vibrations are passed on to tiny bones in your ear called ossicles, through the semicircular canals and to the cochlea.

70
Q

What does the cochlea do

A

Turns these vibrations into electrical signals which get sent to your brain and allow you to sense (hear) the sound

71
Q

What range of frequencies can humans here

A

20Hz - 20kHz

72
Q

What limits human hearing

A
  • The size and shape of our ear drum
  • the structure of all parts within the ear that vibrate to transfer the energy from the sound wave.
73
Q

When are sound waves reflected

A

Sound waves will be reflected by hard surfaces. Echoes are just reflected sound waves.

74
Q

When are sound waves refracted

A

Sound waves will refract when they enter different mediums. As they enter denser material they speed up.

75
Q

Why does the speed of a sound wave change when it enters a different medium

A

When a wave travels into a different medium, it’s wavelength changes but it’s frequency remains the same so its speed must also change.

76
Q

What is ultrasound

A

A sound with frequency higher than 20,000Hz. It is an electrical device that produces electrical oscillations over a range of frequencies.

77
Q

How do ultrasound waves work

A

Point a pulse of ultrasound at an object, and wherever there are boundaries between one substance and another, some of the ultrasound gets reflected back

78
Q

What is ultrasound used in

A

Medical imaging eg. pre-natal scanning
Industrial imaging eg. finding flaws in materials

79
Q

How is ultrasound used in medical imaging

A
  • Ultrasound waves can be passed through the body, but whenever they reach a boundary between two different media (like fluid in the womb and skin of the foetus) some of the wave is reflected back and detected
    The exact timings and distribution of these echoes are processed by a computer to produce a video image of a foetus
80
Q

How is ultrasound used in industrial imaging

A

Ultrasound waves entering a material will usually be reflected by the far side of the material. If there is a flaw such as a crack inside the object the wave will be reflected sooner.

81
Q

What is echo sounding

A

Uses high frequency sound waves to help boats and submarines find out the depth of the water that they are in, or to locate objects in deep water.

82
Q

What thing scan happen when a wave reaches a boundary between materials

A
  • the wave can completely reflect
  • the wave can partially reflect
  • the wave may continue travelling in the same direction but at a different speed
  • the wave may be refracted
83
Q

How are seismic waves produced

A

When there’s an earthquake somewhere, it produces seismic waves which travel out through the Earth

84
Q

How do we detect seismic waves

A

We detect seismic waves all over the surface of the planet, using seismometers

85
Q

What happens to seismic waves when they reach a boundary

A

When seismic waves reach a boundary between different layers of material inside theEarth, some waves will be absorbed and some will be refracted.

86
Q

What happens if seismic waves are refracted

A

They change speed gradally,resulting in a curved path

87
Q

2 types of seismic waves

A

P-waves and S-waves

88
Q

Differences between P waves and S waves

A
  • P waves can travel through the Earth’s core, but S-waves can’t
  • P waves are longitudinal ad S waves are transverse
  • P waves can travel through solids and liquids but S-waves can’t travel through liquids
  • P -waves travel faster than S-waves
89
Q

What is a perfect black body

A

An object that absorbs all of the radiation that hit it. No radiation is reflected or transmitted. They are alos the best possible emitters of radiation.

90
Q

Relationship between temperature and intensity

A

As the temperature of an object increases, the intensity of every emitted wavelength increases.

91
Q

How does wavelength effect intensity

A

The intensity increases more rapidly for shorter wavelengths than linger wavelengths. This causes the peak wavelength to decrease.

92
Q

What does the overall temperature of the Earth depend on

A

The amount of radiation it reflects, absorbs and emits

93
Q

what colour is the best at absorbing and emitting infrared radiation

A

A black surface is better at absorbing and emitting radiation than a white one, and a matte surface is better at absorbing and emitting radiation than a shiny one

94
Q
A
95
Q
A

.. (48 decks)

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