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1
Q
A
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2
Q

What is an electric field?

A

The region where a charged object would experience a force

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3
Q

How is an electric field represented?

A

Using field lines

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4
Q

What does the direction of a field line show?

A

The direction of the force that would act on a small positive charge at that point

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5
Q

What does the spacing of field lines show?

A

The strength of the force.

The closer together the lines, the stronger the force

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6
Q

What is a uniform field?

A

A field for a force that has a constant size

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7
Q

What direction do field lines point when an object is positively charged?

A

Field lines point outwards because like charges repel

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8
Q

What direction do field lines point when an object is negatively charged?

A

Field lines point inwards because unlike charges attract

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9
Q

What happens to field lines as you move away from the charged object?

A

Field lines spread out as you move away, so the force becomes weaker

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10
Q

How does a ‘Van de Graff’ generator work?

A

A charge builds up on the dome due to electrons being rubbed off by the belt. If charge is big enough then the voltage comes high enough to ionise the air molecules so electrons jump down to earth = electric current

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11
Q

Dangers with static electricity when refuelling?

A

Fuel gains electrons from pipe so pipe is positive and fuel negative. Resulting voltage may cause a spark.

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12
Q

Solutions for static electricity when refuelling?

A

Earth the fuel tank with a copper rod or connect the tanker to a place by a copper conductor

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13
Q

How does paint spraying work?

A

Spray gun is charged and so are the paint particles, particles repel each other giving a fine spray. Object is charged opposite to paint so object attracts paint = even coat

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14
Q

What is an electrostatic dust precipitator?

A

A mechanism that remove smoke, dust particles etc. from chimneys

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15
Q

How do electrostatic dust precipitators work?

A

Dust particles gain charge as they pass through a grid

Dust particles are attracted to plates

Dust falls down the chimney when the particles are heavy enough or the plates are knocked

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16
Q

What does the pressure of a gas depend on?

A

mass of molecules

speed of molecules - hitting walls more often

how many molecules - more molecules to hit the walls

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17
Q

What happens when the volume of a gas decreases while the temperature stays the same?

A

The average speed stays the same but the molecules hit the walls more often

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18
Q

What does Boyles law state?

A

The pressure of a fixed mass of gas at a constant temperature is inversely proportional to its volume

pV=constant

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19
Q

pV=constant or…

A

p1V1=p2V2

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20
Q

How is gamma used for tracers in medicine?

A

Gamma radiation should be emitted from the source injected into the patient, so it can be detected outside the body

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21
Q

Why isn’t alpha used for tracers in medicine?

A

Would be too dangerous as the ionisation it causes could mutate cells and cause cancer

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22
Q

How is beta used for leak detection in pipes?

A

The radioactive isotope is injected into the pipe. The outside of the pipe is checked with a Geiger-Muller detector to find areas of high radioactivity - where the pipe is leaking

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23
Q

Why is beta used for leak detection in pipes?

A

It has a short half life so the material doesn’t become a long term problem. It has to be detected through the metal as well as the earth

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24
Q

Why is gamma used in radiotherapy?

A

Gamma kills cancer cells

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25
Q

Why is gamma used in food irradiation?

A

Because gamma keeps it fresh for longer as it kills bacteria or fungi

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26
Q

What happens when there are more nuclei in a sample in terms of half life?

A

When there are more nuclei, more are likely to decay in one half life, so the higher the count rate will be

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27
Q

What is the half life of a radioactive isotope?

A

• The average time it takes for the number of nuclei of the isotope in a sample to half

or

• The time it takes for the count rate from a sample containing the isotope to fall to half its initial level

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28
Q

What is the net decline of a radioactive sample?

A

The fraction of nuclei that have decayed in a certain time

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29
Q

How is the net decline of a radioactive sample portrayed?

A

Fraction, ratio, percentage

doesn’t have a unit

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30
Q

What is the half life required when sterilising medical instruments?

A

Long - years

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31
Q

What is the half life required when using medical tracers?

A

Short - days

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32
Q

What is the half life required when using a thickness monitor?

A

Long - years

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33
Q

What is the half life required when using industrial tracers?

A

Short - days

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34
Q

What is the half life required when using a smoke alarm?

A

Long - years

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35
Q

When does a nucleus become unstable?

A

When it possesses either too many or too few neutrons compared to the number of protons

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36
Q

What is radiation detected with ?

A

A Geiger counter

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37
Q

Define half life using the idea of activity

A

The time it takes for activity to half from its original value

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38
Q

Define half life using the idea of count rate

A

The time it takes for count rate to half from its original value

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39
Q

Define half life using the idea of undecayed atoms left in the source

A

The time it take for half of the nuclei present to decay

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40
Q

How is nuclear radiation used in medicine for imaging?

A
  • radioactive tracers - imaging flows

* gamma cameras - imaging internal organs

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41
Q

What do radioactive tracers image?

A

Flows inside the body

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42
Q

What do gamma cameras image?

A

Internal organs

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43
Q

Why is imaging using radioactive radiation important?

A

To help with diagnosis

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44
Q

Why is nuclear radiation used in medicine?

A

For treatment; to destroy cancer cells

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45
Q

What processes using nuclear radiation help with diagnosis?

A
  • radioactive tracers

* gamma cameras

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46
Q

What processes using nuclear radiation help with treatment?

A
  • gamma radiotherapy

* radioactive implants

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47
Q

What are radioactive tracers used for?

A

To trace the flow of a substance through an organ

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48
Q

How do radioactive tracers work?

A
  • a small amount of radioactive material is put into the patients body
  • tracer is given time to move through body
  • radioactive detector is positioned to detect radiation outside the body
  • multiple images are taken to show progress of tracer over time
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49
Q

How is radioactive material put into a patients body to be used as a tracer?

A

By ingestion or injection

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50
Q

What type of radiation is used in medical tracing?

A

Gamma

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51
Q

Why is gamma used in medical tracing?

A

It is the least ionising and the most penetrating, meaning it can leave the body eventually

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52
Q

Why isn’t alpha used in medical tracing?

A

It can’t be detected outside the body and is very ionising so would damage cells as it moved through the bloody

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53
Q

What are the properties of gamma that ensure medical tracing is not harmful to the patient?

A

Gamma is not ionising, has a short half life and is not toxic

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54
Q

What does a gamma camera do?

A

Images internal organs

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55
Q

How does a gamma camera work?

A
  • a radioactive isotope (gamma emitting) is objected into the patient
  • the isotope concentrates in the organ
  • a gamma camera is positioned over the area emitting gamma
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56
Q

What are gamma cameras made from?

A

A crystal scintillator (sodium iodide)

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57
Q

What happens when gamma hits a crystal scintillator?

A

It produces a burst of light

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58
Q

What do photo multiplier tubes do?

A

Convert energy in electrical signals - which are fed to a computer to produce an image

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59
Q

What does the lead grid do in a gamma camera?

A

Acts as a collinator - only allows gamma aligned with the holes to hit the crystal, making image sharper

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60
Q

What is a collinator used for in a gamma camera?

A

To make the image sharper, less blurred

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61
Q

What is the process happening inside a gamma camera to produce an image?

A
  • gamma rays hit a crystal scintillator and crystal produces a burst of light
  • bursts of light are picked up by a photo multiplier which convert energy to electrical signals
  • the electrical signals are sent to a computer to produce an image
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62
Q

What can ionising radiation do to cells?

A

Low doses - damage cells

High doses - destroy cells

This can lead to cancer

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63
Q

How are cancer cells destroyed in a tumour?

A

Gamma radiation in narrow beams

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64
Q

Where is radiation emitted from in radiotherapy?

A

A radioactive isotope of cobalt

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65
Q

What is the half live of the radioactive isotope of cobalt?

A

Five years

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66
Q

Why are narrow beams used in radiotherapy?

A

So that no tissue before the area that is being treated becomes damaged

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67
Q

How do narrow beams of gamma destroy a tumour?

A

Lots of beams are shone from different angles to overlap on the problem area

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68
Q

Why is gamma used in radiotherapy?

A

It can damage deep inside the body - it is very penetrating - and can escape the body easily

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69
Q

Why is a half life of five years suitable for gamma radiotherapy?

A

It lasts for long enough so it doesn’t need to be replaced and the dose each patient receives doesn’t decrease

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70
Q

What are gamma knives used for?

A

To accurately focus many beams of gamma radiation on one or more brain tumours

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71
Q

What are the beams of radiation in gamma knives life?

A
  • very low intensity

* approximately 200 beams - concentrated on a small volume very accurately

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72
Q

What are radioactive implants used for?

A

To attack the tumour from inside the body

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73
Q

How do radioactive implants work?

A

The sources of radiation are placed directly inside the tumour or nearly tissue

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74
Q

How long can radioactive implants stay in for?

A

Hours or days due to low dose rate sources

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75
Q

What type of radiation can radioactive implants emit?

A

Beta because they are more local to the tumour and are more ionising than gamma

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76
Q

What is a suitable half life for a radioactive implant?

A

A few weeks:

  • enough time for radiation dose to be low for an extended period
  • not long enough to stay active in patient after it’s needed
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77
Q

Advantages of radioactive implants?

A
  • therapy over longer period compared to external beam therapy
  • radiation more localised - especially with beta
  • patient can spend less time in hospital
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78
Q

Disadvantages of radioactive implants?

A
  • small risk of exposure of radiation to family and friends

* only early stage diseases and small tumours can be treated

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79
Q

What is nuclear fission?

A

The splitting of a large nucleus into two smaller nuclei (‘daughters’) while releasing energy

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80
Q

Which nuclei are split in fission reactions?

A

Usually uranium-235 but also plutonium-239

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81
Q

What is induced fission?

A

When a reaction occurs due to a neutron being fired at a uranium nucleus

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82
Q

What do fission reactions release?

A
  • two or three neutrons at high speeds (these are used in further reactions)
  • energy in the form of radiation and kinetic energy of the fission neutrons
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83
Q

What form of energy is released in fission?

A
  • radiation

* kinetic - of the neutrons and the fragment nuclei

84
Q

What happens in a chain reaction?

A

Each reaction causes more reactions which cause more reactions etc.

85
Q

What is the energy produced in fission used for?

A

Heats water and turns it into steam -> turns turbine -> turns generator transforms kinetic to electrical energy

86
Q

How is the output of a nuclear fission power station made stable?

A

The energy released must be constant and not grow rapidly like in an uncontrolled chain reaction

87
Q

In a nuclear reactor, what is the function of the control rods?

A

To absorb surplus neutrons to keep chain reaction under control

88
Q

In a nuclear reactor, what is the function of the moderator?

A

To slow the fission neutrons down

89
Q

Why is water used as a moderator in a nuclear reactor?

A

Fission neutrons are slowed down by collisions with the atoms in the water molecules

90
Q

What is a fission neutron?

A

A neutron released when a nucleus undergoes nuclear fission

91
Q

In a nuclear reactor, what is the function of the coolant?

A

Water - transfers heat so radioactive water is not turned to steam

92
Q

In a nuclear reactor, why is the reactor core in a thick steel vessel surrounded by concrete walls?

A

To withstand high temperature and pressure. Walls absorb gamma radiation that escapes steel vessel

93
Q

In a nuclear reactor, why does the coolant circulate through sealed pipes to and from a heat exchanger?

A

So contaminated water is not turned to steam and enters the atmosphere

94
Q

In a nuclear reactor, why may the control rods need to be inserted completely into the reactor core?

A

So there isn’t too much energy being released from uncontrolled fission

95
Q

What is nuclear fusion?

A

When two small nuclei collide and fuse to form a larger nucleus, releasing energy

96
Q

What process powers the sun and the stars?

A

Nuclear fusion

97
Q

How is the gas in a fusion reactor heated?

A

By passing an electric current through it

98
Q

What happens when the gas in a fusion reactor gets very hot?

A

It forms a plasma of small nuclei

99
Q

How is the plasma contained in a fusion reactor?

A

Using a magnetic field to prevent it from touching the container walls

100
Q

What is one of the products when hydrogen nuclei fuse?

A

Helium

101
Q

What happens in a fusion reactor is the plasma touches the sides of the container?

A

The plasma would cool down, and fusion would stop

102
Q

In fusion, what do nuclei need to fuse?

A

Enough kinetic energy

103
Q

In fusion, what happens if nuclei do not have enough kinetic energy to fuse?

A

They will repel each other and not fuse

104
Q

Advantages of nuclear fission?

A
  • concentrated source of energy
  • no polluting gases - energy is released from nuclear reactions not combustion
  • supply of uranium for many years
  • reliable - 24/7 (doesn’t depend on weather like renewables)
105
Q

Disadvantages of nuclear fission?

A
  • produces radioactive waste
  • chain reaction must be controlled
  • non-renewable
106
Q

Advantages of nuclear fusion?

A
  • produces very little radioactive waste - safer
  • no chain reaction to control - safer
  • even more concentrated energy
  • fuel readily available (hydrogen in water)
  • renewable
  • hydrogen is cheap
107
Q

Disadvantages of nuclear fusion?

A

• not yet viable - fusion on earth needs more energy input than output (need 5 million amp current!)

108
Q

Which is a more concentrated source of energy: fission or fusion?

A

Fusion

109
Q

Which type of nuclei fuse in the sun?

A

Hydrogen

110
Q

Which type of nuclei are formed in the sun?

A

Helium

111
Q

What equation shows Newtons 2nd law of motion?

A

F = m a

112
Q

How is thinking distance decreased?

A

Friction reduced - wet roads, worn tyres or brakes

113
Q

How is braking distance decreased?

A

Larger mass of car (more inertia means its harder to stop)

114
Q

How is thinking distance shown on a graph?

A

Area of the rectangle underneath the graph

115
Q

How is braking distance shown on a graph?

A

Area of the triangle underneath the graph

116
Q

What are the two SUVAT equations?

A

v = u + at

v2 = u2 - 2as

117
Q

What are the two ways of increasing the turning effect of a force?

A
  • increase the size of the force

* increase the distance from the pivot

118
Q

What is the turning effect of a force called?

A

A moment

119
Q

What is the equation to calculate the size of a moment?

A

M=Fd

120
Q

What are moments measured in?

A

Nm

121
Q

What does the pressure of a liquid depend on?

A

The depth and the density

122
Q

What is the equation for the pressure at a certain depth due to the column of liquid?

A

pressure = depth x field strength x density

123
Q

What is the nature of liquid pressures at different places, but at the same depth?

A

The pressure acts in all directions and is the same depth

124
Q

What is the nature of liquid pressures at different depths?

A

The greater depth, the higher the pressure so the water is pushed down with a greater force and has a bigger horizontal range

125
Q

What is a gear?

A

A rotating machine with cogs that mesh with another toothed part to transmit a moment

126
Q

What do gears act as?

A

A force multiplier

127
Q

What is a force multiplier?

A

Machines designed to increase the size of the force

128
Q

What is a distance multiplier?

A

Machines designed to increase the distance or speed with which something moves

129
Q

What effort and load do force multipliers involve?

A
  • small effort (input force)

* larger load (output force)

130
Q

Equation for mechanical advantage?

A

load / effort

131
Q

Example of a force multiplier?

A

Lever with a distance from pivot to effort 3 times greater than distance from pivot to load - mechanical advantage is 3

132
Q

How is a bike an example of a distance or speed multiplier?

A

Slow movement of pedals produces a much faster rotation of the wheels

133
Q

What effort and load do distance multipliers involve?

A
  • small movement of effort

* large movement of load

134
Q

How is energy shown to be conserved in gears?

A

Work done by input gear = Work done by output gear

135
Q

Why can a machine not be a force and distance multiplier at the same time?

A

As energy is conserved, if force is doubled the distance is halved and vice versa

136
Q

What are levers used to do?

A

Lift heavy masses with the least amount of effort

137
Q

What three things can gears do when passing power from one wheel to another?

A
  • increase speed - first gear has more teeth than second so second has to turn faster to keep up
  • increase force - second gear has more teeth than first so second turns slower but with more force
  • change direction - when gears mesh they always turn in the opposite direction
138
Q

In a hydraulic system, a smaller force on the master (effort) piston will produce what force on the slave (load) piston?

A

A larger force as the pressure of the liquid is constant - acting as a force multiplier

139
Q

What is the ratio of in levers?

A

Lengths

140
Q

What is the ratio of in gears?

A

Number of teeth

141
Q

What is the ratio of in hydraulics?

A

Cross sectional areas

142
Q

Equation for levers?

A

Fb/Fa = Lb/La

143
Q

Equation for gears?

A

Fb/Fa = Nb/Na

144
Q

Equation for hydraulics?

A

Fb/Fa = Ab/Aa

145
Q

What is the atmosphere?

A

A thin layer of air around the earth

146
Q

What happens at a greater altitude?

A
  • the less dense the atmosphere

* the lower the atmospheric pressure

147
Q

Why is the atmospheric pressure lower at greater altitudes?

A
  • at higher altitudes there is less air above a surface
  • so there is a smaller weight of air acting on the surface
  • p=F/A and F is reduced so p will be smaller
148
Q

How is upthrust created?

A

When the bottom surface of an object is submerged in a liquid it experiences a greater pressure than the top surface

149
Q

When does an object float?

A

When its weight = upthrust / weight of fluid displaced

150
Q

What is upthrust equal to?

A

The weight of the liquid displaced

151
Q

What does force equal in terms of the change in momentum?

A

Force = change in momentum / time taken

152
Q

When are ultrasound waves reflected?

A

When they reach a boundary between two different media

153
Q

How do you determine how far away a boundary is?

A

How long the reflections take to reach the detector

154
Q

What surface is the best emitter of infrared radiation?

A

Matte black surfaces

155
Q

What surface is the worst emitter of infrared radiation?

A

Silver (shiny) surfaces

156
Q

Best materials to emit infrared radiation? Best to worst

A

Matte black, shiny black, white, silver

157
Q

Which kettle will cool down faster: black or metallic?

A

Black because it will emit more radiation

158
Q

What direction does heat energy flow in?

A

From a hot object to a cooler one

159
Q

What do good emitters also act as?

A

Good absorbers

160
Q

What surface is the best absorber of infrared radiation?

A

Matte black surfaces

161
Q

What surface is the worst absorber of infrared radiation?

A

Silver surfaces

162
Q

Best materials to absorb infrared radiation? Best to worst

A

Matte black, shiny black, white, silver

163
Q

Why are shiny surfaces the worst absorbers?

A

They reflect most of the radiation away

164
Q

Why do solar panels have a black outer layer?

A

So it can absorb heat

165
Q

Why are firefighters suits shiny?

A

They are the worst absorbers, the the best reflectors

166
Q

Why is the back of a solar panel silver?

A

Reflect heat back onto pipes

167
Q

Why are premature babies wrapped in silver blankets?

A

Its the worst emitter, so reduces the amount of heat that they lose

168
Q

Why are radiators in car engines black?

A

It’s the best emitter

169
Q

What is a perfect black body?

A

An object that absorbs all the radiation that hits it

170
Q

What does a perfect black body not do?

A

Reflect or transmit any radiation

171
Q

What is the radiation emitted by a black body called?

A

Black body radiation

172
Q

What is black body radiation?

A

The radiation emitted by a black body

173
Q

What are the two major types of lens?

A
  • concave

* convex

174
Q

What can concave lenses also be known as?

A

Diverging lenses

175
Q

What can convex lenses also be known as?

A

Converging lenses

176
Q

When is there a principal focus?

A

When the light rays are parallel

177
Q

In a convex lens, how does the thickness of the lens affect the focal length?

A

The thicker the lens, the shorter the focal length

178
Q

What is the shape of a converging lens?

A

It is thicker at the centre than the edges

179
Q

What is the shape of a diverging lens?

A

It is thinner at the centre than the edges

180
Q

How is magnification calculated?

A

magnification = image height / object height

181
Q

If the image is larger than the object what is the magnification equal to?

A

greater than 1

182
Q

If the image is smaller than the object what is the magnification equal to?

A

less than 1

183
Q

What can the image in a convex lens be?

A
  • real or virtual
  • magnified or diminished
  • upright or inverted
184
Q

How is the image transformed in a camera?

A

(convex lens)

  • diminished
  • inverted
  • real
185
Q

How is the image transformed in a projector?

A

(convex lens)

  • magnified
  • inverted
  • real
186
Q

How is the image transformed in a magnifying glass?

A

(convex lens)

  • magnified
  • upright
  • virtual
187
Q

What type of images do convex lenses give?

A
  • virtual
  • upright
  • diminished
188
Q

What happens in a convex lens when the object moves further away from the lens?

A

The image gets smaller and moves away from the lens

189
Q

How is short-sightedness corrected?

A

The eyeball is elongated so needs a concave lens

190
Q

How is long-sightedness corrected?

A

Convex lens

191
Q

Why does white light spread out into colours after it passes through a glass pyramid?

A

The different wavelengths experiences different changes in speed as they enter and leave the glass so refract by different amounts

192
Q

Which colours are refracted the most and the least?

A
  • red is refracted the least

* violet is refracted the most

193
Q

What are the primary colours of light?

A

Red, green, blue

194
Q

What are the secondary colours of light?

A

Yellow, cyan, magenta

195
Q

What does green and blue light create?

A

Cyan light

196
Q

What does green and red light create?

A

Yellow light

197
Q

What does green and red light create?

A

Magenta light

198
Q

What does a filter do?

A

Only allows a small range of wavelengths to pass through

199
Q

What does a red filter do?

A

Only allows red light through and absorbs blue and green light

200
Q

What are opaque objects?

A

Those that do not transmit light

201
Q

What does the colour that an objects appears depend on?

A

Which wavelengths are most strongly reflected

202
Q

Why do objects appear white?

A

They reflect all of the wavelengths of visible light equally

203
Q

Why does a red object look black through a blue filter?

A

A red object only reflects red light and the blue filter only transmits blue light, so only blue light shines on the red object and it is absorbed so it appears black

204
Q

How is a light ray reflected by flat foil?

A

Reflected in a single direction (specular reflection)

205
Q

How is a light ray reflected by crumpled foil?

A

Scattered (diffuse reflection)

AQA GCSE Physics (13 decks)

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