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Physics > Waves, Electromagnetism and Space > Flashcards

Waves, Electromagnetism and Space Flashcards

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1
Q

What are waves used for?

A

To transfer energy and information

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2
Q

What are transverse wave?

A
  • waves that oscillate perpendicular to the direction of energy transfer

_/^_/^_/^_/^_

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3
Q

Give an example of transverse waves

A
  • ripples on the surface of water

- all electromagnetic waves

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4
Q

What are longitudinal waves?

A

Waves that oscillate parallel to the direction of energy transfer

/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

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5
Q

Give an example of longitudinal waves

A
  • sound waves in air
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6
Q

What do mechanical waves need?

A

A medium to travel through

- can be transverse or longitudinal

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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 un disturbed position
- height or depth of the wave crest from the center line

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8
Q

What is the frequency of a wave?

A

The number of waves passing a point per second

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9
Q

What is the wavelength of a wave?

A

The distance from a point on the wave to the equivalent point on the next wave
- peak to peak or trough to trough

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10
Q

Where does refraction occur?

A

At a boundary between two differnent materials

- because the speed and wavelength change there

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11
Q

What can happen to waves at a boundary between two materials?

A

They can be transmitted or absorbed

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12
Q

What are sound waves?

A

Vibrations that travel through a substance

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13
Q

Sound waves cannot travel through …

A

.. a vacuum

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14
Q

How do you investigate waves?

A
  • a ripple tank =water waves
  • a stretched string = waves in a solid
  • a signal generator/ loudspeaker = sound waves
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15
Q

What increases the pitch of a note?

A

An increase in the frequency of the wave

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16
Q

What changes the volume of a note?

A 
LOUD = increased amplitude
QUIET = decreased amplitude
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17
Q

How do we hear sound?

A

Sound waves cause the ear drum to vibrate, which sends signals to the brain

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18
Q

What are ultrasound waves?

A

Sound waves with a frequency above 20,000Hz

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19
Q

Ultrasound waves are partly …

A

.. reflected at a boundary between two different types of body tissue

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20
Q

Why are ultrasound scans safer than x-rays?

A

They are non-ionising

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21
Q

What are seismic waves?

A

Waves that travel through the earth

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22
Q

When are seismic waves produced?

A

In earthquakes where they spread out from the epicentre

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23
Q

What type of waves are seismic waves?

A

Primary = longitudinal
/\/\/\/\/\/\/\/\
Secondary = transverse
_/^_/^_/^_/^_

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24
Q

The earth is made up of …

A
  • a liquid inner core
  • a solid outer core
  • the mantle
  • the crust
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25
Q

The electromagnetic spectrum

In order of decreasing wavelength and increasing frequency

A 
Radio waves
Microwaves
Infrared radiation
Visible light
Ultraviolet waves
Xrays
Gamma rays
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26
Q

How to remember the order of the electromagnetic spectrum:

A 
Randy
Men
Inject
Viagra
Until
Xplosive
Growth
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27
Q

Electromagnetic waves transfer energy from a source to …

A

.. an absorber

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28
Q

The human eye can only detect …

A

.. visible light.

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29
Q

White light contains …

A

.. all the colours of the visible light spectrum.

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30
Q

What is infrared radiation used for?

A

Carrying signals from remote control handsets and inside optical fibres.

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31
Q

What are microwaves used for?

A

Carrying satellite TV programmes and mobile phone calls

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32
Q

What are radio waves used for?

A

For radio and TV broadcasting, radio communications and mobile phone calls

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33
Q

How can electromagnetic radiation be hazardous?

A
  • Microwaves and Radiowaves can heat the internal parts of people’s bodies
  • Infrared radiation can cause skin burns
  • Ultraviolet waves can harm the skin and the eyes
  • Xrays and Gamma rays damage living tissue when they pass through it
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34
Q

Further research needs to be done to see if …

A

.. mobile phones are safe to use

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35
Q

What are carrier waves?

A

Waves that are used to carry information by varying their amplitude

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36
Q

What does the wavelength of radio waves affect?

A
  • how far they travel
  • how much they spread
  • how much information they carry
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37
Q

What are optical fibres?

A

Very thin transparent fibres that are used to transmit communication signals by light and infrared radiation

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38
Q

What are Xrays used for?

A

To make xray images in hospitals

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39
Q

What are Gamma rays used for?

A

To kill harmful bacteria in food
To sterilise surgical equipment
To kill cancer cells

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40
Q

What does ionising radiation do to uncharged atoms?

A

Charge them

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41
Q

Where and why are Xrays used?

A

In hospitals to :

  • make images of internal body parts
  • destroy tumours at or near the body surface
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42
Q

What are Xrays absorbed by?

A
  • More by bones and teeth

- Less by soft tissue

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43
Q

What is the Normal?

A

A line drawn perpendicular to the mirror

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44
Q

What does the law of reflection state?

A

Angle of incidence = Angle of reflection

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45
Q

What is the angle of incidence?

A

The angle between the normal and the incident ray

46
Q

What is the angle of reflection?

A

The angle between the normal and the reflection line

47
Q

What is specular reflection?

A

Reflection in a single direction without scattering

48
Q

What is diffuse reflection?

A

Reflection from a rough surface that scatters the light

49
Q

What is refraction?

A

The change in direction of waves when they travel across a boundary from one medium to another

50
Q

What happens to the angle of refraction when a light ray refracts as it travels into glass?

A

It is less than the angle of incidence

51
Q

What happens to the angle of refraction when a light ray refracts as it travels from glass into air?

A

It is more than the angle of incidence

52
Q

What happens to the wavelength of light across the visible spectrum?

A

It increases from red to violet

53
Q

What does the colour of a surface depend on?

A

The pigments of the surface materials

The wavelengths of light the pigments absorb

54
Q

A translucent object lets light pass through it but …

A

.. scatters or refracts the ligh inside it

55
Q

A transparent object lets all the light that enters it pass through it and …

A

.. does not scatter or refract the light inside the object

56
Q

What does a convex lens focus?

A

Parallel rays to a point called to principle focus

57
Q

What does a concave lens do?

A

Makes parallel rays spread out as if they had come from a point called the principle focus

58
Q

When is a real image formed in a convex lens?

A

When the object is further away than the principle focus

59
Q

When is a virtual image formed by a convex lens?

A

When the object is nearer than the principle focus

60
Q

What can a rag diagram be drawn to find?

A

The position and nature of an image lens

61
Q

Cameras contain convex lenses to form …

A

.. real images of objects

62
Q

A magnifying glass is a …

A

.. convex lens that is used to form a virtual image of an object

63
Q

Like poles …

A

.. repel

64
Q

Unlike poles …

A

.. attract

65
Q

Where do magnetic feild lines form around a bar magnet?

A

Curve around the bar from the north pole to the south pole

66
Q

What is induced magnetism?

A

Magnetism created in an unmagnetised magnetic material when the material is placed in the magnetic field

67
Q

Why is steel used instead of iron to make permanent magnets?

A

Steel doesn’t lose its magnetism easily, whereas iron does

68
Q

The magnetic field lines around a wire are …

A

.. circles centred on the wire in a plane perpendicular to the wire

69
Q

The magnetic field lines in a solenoid are …

A

.. parallel to its axis and all travel in the same direction

70
Q

What is a uniform magnetic field?

A

One where the magnetic field lines are parallel

71
Q

What does increasing the current do to the magnetic field?

A

Makes it stronger

72
Q

What happens to the magnetic field lines when you reverse the direction of the current?

A

They reverse their direction

73
Q

What is an electromagnet?

A

A solenoid that has an iron core. It consists of an insulating wire wrapped around an iron bar.

74
Q

Where are electomagnets used?

A
  • scrapyard cranes
  • circuit breakers
  • electric bells
  • relays
75
Q

How do electromagnets work?

A

They attract an iron armature, which opens a switch

76
Q

How is the force increased in the motor effect?

A

If the current or magnetic field strength of the conductor is increased

77
Q

How is the force reversed in the motor effect?

A

If the direction of the current or the magnetic field is reversed

78
Q

What is magnetic flux density?

A

A measure of the strength of a magnetic field

79
Q

What is in an electric motor?

A

A coil that turns when the current is passed through it

80
Q

What is the generator effect?

A

The effect of inducing a potential difference using a magnetic field

81
Q

What happens when a conductor crosses through the lines of a magnetic field?

A

A potential difference is induced across the ends of the conductor

82
Q

The direction of an induced current always opposes the …

A

.. original change that caused it

83
Q

What is a simple a.c. generator made up of?

A

A coil that spins in a uniform magnetic field

84
Q

What is a simple d.c. generator made up of?

A

A split-ring commutator instead if two slip rings

85
Q

What are transformers used for?

A

To increase or decrease the size of an alternating potential difference

86
Q

The size of alternating potential difference is increased by …

A

.. a step-up transformer.

87
Q

The size of alternating potential difference is decreased by …

A

.. a step-down transformer.

88
Q

Why do transformers only work with an alternating current?

A

Because a changing magnetic field is necessary to induce a.c. in the secondary coil

89
Q

What does a transformer have?

A
  • a primary coil
  • a secondary coil
  • an iron core
90
Q

How is a high grid potential difference made more efficient?

A

By reducing it to the current needed, therefore reducing power loss

91
Q

How did the gas and dust clouds formed by the Solar System become more concentrated?

A

Gravitational attraction

92
Q

What is a protostar?

A

A concentration of gas and dust that becomes hot enough to cause nuclear fussion

93
Q

Why is energy released inside a star?

A

Because of hydrogen nuclei fusing together to form helium nuclei.

94
Q

Why is the Sun stable?

A

Because gravitational forces acting inwards balance the forces of nuclear fusion energy in the core acting outwards.

95
Q

When do stars become unstable?

A

When they have no more hydrogen nuclei that can fuse together.

96
Q

Which stars have roughly the same mass as the Sun

A
  • protostar
  • main-sequence star
  • red supergiant
  • red giant
  • white dwarf
  • black dwarf
97
Q

The Sun will eventually become a …

A

.. black dwarf.

98
Q

What is a supernova?

A

The explosion of a red supergiant after it collapses.

99
Q

What keeps a planet moving along its orbit?

A

The force of gravity between a planet and the sun.

100
Q

What keeps the satellite moving along its orbit?

A

The force of gravity between the Earth and a satellite.

101
Q

Where is the force of gravity in an orbiting body in a circular orbit?

A

Towards the centre of thr circle.

102
Q

What happens as a body in a circular orbit moves around the orbit?

A
  • the magnitude of its velocity stays the same
  • the direction of its velocity continually changes and is always at right angles to the direction of the force
  • it experiences an acceleration towards the center of the circle
103
Q

What must happen for a small body to stay in orbit at a particular point?

A

It must move at a particular speed around a larger body.

104
Q

What is a red-shift of a distant galaxy?

A

The shift to longer wavelengths of the light from a galaxy because it is moving away from you.

105
Q

The faster a galaxy is moving away from you, the …

A

.. greater its red-shift is.

106
Q

The further away a distant galaxy is from you, the …

A

.. greater its red-shift is.

107
Q

Why are distant galaxies moving from here?

A

Because the universe is expanding.

108
Q

What created the universe?

A

The Big Bang.

  • a massive explosion from a very small and extremely hot and dense region
  • space, time and matter were created as a result
109
Q

The universe has been expanding since …

A

.. the Big Bang.

110
Q

What is cosmic microwave background radiation?

A

Electromagnetic radiation that was created just after the Big Bang.

111
Q

What evidence is there that the universe is expanding?

A

Red-shifts of the distant galaxies mean that they are moving further away.

Physics (5 decks)

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