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Physics > Physics 4 - Waves electromagnetism, and space (P12 - P16) > Flashcards

Physics 4 - Waves electromagnetism, and space (P12 - P16) Flashcards

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1
Q

What do Transverse Waves do? Give an example.

A

Oscillate perpendicular to the direction of energy transfer of the waves. All electromagnetic waves are Transverse.

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2
Q

What do Longitudinal Waves do? Give an example.

A

Oscillate parallel to the direction of energy transfer of the waves. Sound waves are longitudinal.

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3
Q

What do Mechanical waves do?

A

They need a substance to travel through. They can be transverse or longitudinal.

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4
Q

What is the equation for wave speed?

A

Wave speed (m/s) = Frequency (Hertz Hz) x Wavelength λ (metres m)

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5
Q

What element of waves effects the pitch of soundwaves?

A

Frequency.

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6
Q

What happens to soundwaves if amplitude is increased?

A

The volume increases.

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7
Q

What is the equation for distance travelled by a wave?

A

Distance travelled (m) = speed of ultrasound waves in body tissue (m/s) x time taken (seconds)

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8
Q

What is the equation for the depth of the boundary below the surface that a wave penetrates?

A

The depth of the boundary below the surface (m) = 0.5 x speed of the ultrasound waves (m/s) x time taken (seconds)

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9
Q

What are ultrasound waves?

A

Sound waves with a frequency above the range of human hearing.

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10
Q

What are seismic waves?

A

Waves that travel through the earth’s crust.

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11
Q

Which end of the electromagnetic spectrum has the longest wavelength?

A

Radio waves (The beginning)

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12
Q

What speed do electromagnetic waves travel at?

A

300 million m/s (Speed of light)

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13
Q

What type of light contains all the colours of the visible spectrum?

A

White light.

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14
Q

Which side of the visible light spectrum has the longest wavelength?

A

Red light.

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15
Q

(P14) How do you draw the normal at a point on a mirror?

A

It is a line drawn perpendicular to the mirror.

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16
Q

What is the law of reflection?

A

It states that the angle of incidence = the angle of reflection.

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17
Q

What is the angle of incidence?

A

The angle between the incident ray and the normal

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18
Q

What is the angle of reflection?

A

The angle between the reflected ray and the normal.

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19
Q

What is specular reflection?

A

Reflection in a single direction without scattering. Diffuse reflection is reflection from a rough surface that scatters the light.

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20
Q

What is refraction of light?

A

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

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21
Q

Which is bigger, the angle of refraction or the angle of incidence when a light ray travels from air to glass?

A

The angle of incidence.

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22
Q

Which is bigger, the angle of refraction or the angle of incidence when a light ray travels from glass to air?

A

The angle of refraction.

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23
Q

What does a translucent object do to light rays?

A

Lets light pass through it but scatter or refracts the light inside it.

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24
Q

What does a transparent object do to light rays?

A

Lets all the light that enters pass through it and does not scatter or refract the light.

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25
Q

What does a convex lens do to parallel rays?

A

Focuses them to a point called the principal focus.

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26
Q

What does a concave lens do to parallel rays?

A

Spreads them out as if they had come from a point called the principal focus.

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27
Q

How is a real image formed by a convex lens?

A

If the object is further away than the principal focus.

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28
Q

How is a virtual image formed by a convex lens?

A

If the object is closer than the principal focus.

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29
Q

What is the equation for magnification?

A

Magnification = image height / object height

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30
Q

What is a ray diagram used for?

A

To find the position and nature of an image formed by a lens.

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31
Q

What is the nature of an image formed when an object is placed between a convex lens and its principal focus? (four things)

A

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

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32
Q

What type of lens does a camera have and what is it used for?

A

A convex lens that is used to produce a real image of an object.

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33
Q

What type of lens does a magnifying glass have and what is it used for?

A

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

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34
Q

How do the three rays move in a lens diagram where the object is beyond the principal focus?

A

Ray 1 : Refracted through F1, the principal focus of the lens after reaching the lens. The ray is perpendicular to both the lens and the point of the object. It is parallel to the principal axis.
Ray 2 : Passes through the centre of the lens, its pole, without a change in direction - this is because the lens surfaces at the principal axis are parallel to each other.
Ray 3 : Passes through F, the principal focus of the lens before it reaches the lens, so it is refracted by the lens parallel to the principal axis.

35
Q

How can the magnetic field lines of a bar magnet be illustrated in a diagram?

A

The magnetic field lines of the bar magnet curve around from the north to the south pole.

36
Q

What is induced magnetism?

A

magnetism created in an unmagnetised magnetic material when the material is placed in the magnetic field.

37
Q

Why is steel used to make permanent magnets rather than iron?

A

Because iron is more partial to losing its magnetism than steel is.

38
Q

What is the nature of magnetic field lines around a wire?

A

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

39
Q

What is a solenoid?

A

A coil of insulate wire that is wrapped around an object where a magnetic field is produced. A magnetic field is produced in and around the solenoid when a current is passed through the wire.

40
Q

How are the magnetic field lines of a solenoid illustrated?

A

They are parallel to the solenoid’s axis and are all in the same direction.

41
Q

What does increasing the curent do to a magnetic field?

A

Increases it.

42
Q

What does reversing the direction of an electric current current do to the magnetic field?

A

Reverses the magnetic field lines. This changes the side of the magnet on which each pole resides.

43
Q

What is an electromagnet?

A

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

44
Q

How does an electromagnet work in an electric bell?

A

It attracts an iron armature when a current is passed through it which opens a switch.

45
Q

What is the unit for magnetic flux density?

A

T tesla.

46
Q

What is the equation for magnetic flux density?

A

force, F (N) = Magnetic flux density B (tesla T) x current I (amperes A) x length, l (metres, m)

47
Q

What is magnetic flux density?

A

The measure of strength of the magnetic field.

48
Q

How is the force increased in the motor effect? (Give 3 ways)

A

When the current or the strength of the magnetic field or the length of the conductor is increased.

49
Q

How is the force reversed in the motor effect?

A

If the direction of the current or the magnetic field is reveresed.

50
Q

How does the coil turn in an electric motor?

A

The coil is set between two poles of a magnet, causing it to magnetise to one at all times, the current moving through the coil is reversed every half turn changing the pole that the coil is attracted to, equating in a turning motion.

51
Q

What is the generator effect?

A

The effect of inducing a potential difference (Voltage V) using a magnetic field.

52
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.

53
Q

What does the speed of a conductor as it passes through a magnetic field do to the size of the induced potential difference?

A

The speed is proportional to the size of the induced potential difference.

54
Q

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

A

A coil that spins in a uniform magnetic field.

55
Q

When is the waveform displayed at its peak value on an oscilloscope of an a.c. generator’s induced potential difference?

A

When the sides of the coil cross directly through the magnetic field lines.

56
Q

When is the waveform displayed at zero value on an oscilloscope of an a.c. generator’s induced potential difference?

A

When the sides of the coil move parallel to the field lines.

57
Q

What are transformers used for?

A

To increase or decrease the size of an alternating potential difference.

58
Q

Give the name of both types of transformers and what they do.

A

Step-up transformers increase alternating potential difference and step-down decrease alternating potential difference.

59
Q

What does a transformer consist of?

A

A primary coil, a secondary coil and an iron core.

60
Q

What is the transformer equation?

A

Primary potential difference V (p) / Secondary potential difference V (s) = n (p) / n (s)
n = number of turns on the coil
p/s= primary/secondary coil

61
Q

Which coil turns more in a step down transformer?

A

Primary coil

62
Q

Which coil turns more in a step up transformer?

A

Secondary coil

63
Q

What is the equation that is true in a 100% efficient transformer?

A

V(p) x I(p) = V(s) x I(s)

64
Q

How does a high grid potential difference increase the efficiency of the system?

A

It reduces the current, therefore reducing the power loss of the system.

65
Q

What did the Solar System form from?

A

Has and dust clouds that gradually became more and more concentrated because of gravitational attraction.

66
Q

What is a protostar?

A

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

67
Q

Why is energy released in a star?

A

Because of Hydrogen nuclei fusing together to form helium nuclei.

68
Q

How is the sun stable?

A

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

69
Q

When do stars become unstable?

A

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

70
Q

How are red giants formed?

A

When a star reaches the end of its main-sequence stage by running out of hydrogen nuclei to fuse together in its core, it’s core collapses and it’s outer layers swell out. They also turn red.

71
Q

Which stars have about the same mass as the Sun?

A

Protostar -> main-sequence star -> red giant

-> white dwarf -> black dwarf

72
Q

Which stars are much more massive than the sun?

A

Protostar -> Main-sequence star -> red super-giant -> supernova -> neutron star -> (black hole if enough mass)

73
Q

What is a supernova?

A

The explosion of a red supergiant after it collapses.

74
Q

What does the force of gravity between a planet and the Sun do?

A

Keeps the planet moving along its orbit.

75
Q

What does the force of gravity between a planet and a satellite do?

A

Keeps the satellite moving along its orbit.

76
Q

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

A

Towards the centre of the circle.

77
Q

Name two things that happen when a body in a circular orbit moves around the orbit.

A
  • The magnitude of its velocity does not change.
  • The direction of its velocity continually changes and is always at right angles to the direction of the force so that it experiences an acceleration towards the centre of the circle.
78
Q

What must a small body do to stay in orbit at a particular distance?

A

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

79
Q

What is red shift?

A

Is the shift to longer wavelengths and lower frequencies of the light from the galaxy because it is moving further away from you.

80
Q

What factor increases the red-shift?

A

The faster a distant galaxy is moving away from you.

81
Q

Why does red-shift occur?

A

Because the universe is expanding, causing distant galaxies to be moving away from our own.

82
Q

How did the universe start? (According to the lovely people at AQA)

A

The Big Bang

83
Q

What is Cosmic microwave background radiation? (CMBR)

A

Electromagnetic radiation that was created just after the Big Bang.

Physics (6 decks)

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