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Physics > Modern physics > Flashcards

Modern physics Flashcards

1
Q

3 properties of an electron

A

extremely small mass
has a negative charge
located in orbit around the nucleus of an atom

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2
Q

thermionic emission

A

the emission of electrons from the surface of a hot metal

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3
Q

electrons were originally called

A

cathode rays

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4
Q

what are cathode rays

A

electrons emitted from a cathode

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5
Q

example of electrons emitted from a cathode

A

an old television

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6
Q

who suggested the name electron

A

G J Stoney, irish hysicist

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7
Q

who and when was the charge measured on the electron

A

milikan in 1909 with his oil drop experiment

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8
Q

in a cathode ray tube what does the cathode do

A

electrons are emitted from the cathode by thermionic emission

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9
Q

in a cathode ray tube what does the control grid do

A

by being kept more or less negative (o to -50V) you can control the amount of electrons passing through ie. brightness control

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10
Q

in a cathode ray tube what does the focusing anode do

A

converges the electrons into a narrow beam so that a well defined image is seen on the screen

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11
Q

in a cathode ray tube what does the accelerating anode do?

A

has a potential usually over 1000V. accelerates the electrons to a very high speed

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12
Q

in a cathode ray tube what does the flourescent screen do?

A

when the very fast electrons hit the screen, their kinetic energy is converted to light

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13
Q

what chemical is used on the screen

A

zinc sulfide

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14
Q

Y-plates

A

a pair of charged horizontal metal plates

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15
Q

what do the y-plates do?

A

the electric fields of these plates can deflect the electrons vertically

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16
Q

X-plates

A

a pair of charged vertical metal plates

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17
Q

what do the x-plates do?

A

the electric fields of these plates can deflect the electrons horizontally

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18
Q

2 parts of the deflecting system

A

x plates and y plates

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19
Q

what does the coating of graphite inside of the tube do?

A

conducts the electrons from the screen back to the accelerating anode. The passage of electrons between cathode and anode is maintained

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20
Q

2 uses of a cathode ray tube

A

an old television

a cathode ray oscilloscope

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21
Q

2 medical uses of a cathode ray tube

A

ECG

EEG

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22
Q

what does ECG stand for?

A

electrocardiogram

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23
Q

what does EEG stand for?

A

electroencephalogram

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24
Q

what does an ECG do?

A

displays electrical signals in the heart

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25
Q

what does an EEG do?

A

displays small varying electrical signals in the brain

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26
Q

kinetic energy of an electron

A

1/2 m v squared

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27
Q

work done to accelerate an electron

A

q V

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28
Q

how do you find the speed of an electron accelerated

A

let the gain in kinetic energy equal to the work done to accelerate

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29
Q

how to find the velocity of an electron in a circular orbit in a magnetic field

A

let the force of magnetic field equal the centipetal force

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30
Q

force of magnetic field on electron

A

B q v

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31
Q

centripetal force

A 
     r
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32
Q

set up of demonstration to show photoelectric emission

A

high frequency light falling on a negatively charged plate on a gold leaf electroscope

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33
Q

what happens in the demonstration to show photoelectric emission

A

gold leaf electroscope deflection decreases

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34
Q

in the demonstration to show photoelectric emission, why does the deflection of the gold leaf electroscope decrease

A

electrons are being emitted from the negatively charged metal plate due to the incident light

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35
Q

** definition of photoelectric emission **

A

the emission of electrons from a metal surface using light of a suitable frequency

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36
Q

what do you use to change the frequency of the incident light

A

using special filters

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37
Q

photoelectric emission AKA

A

photoelectric effect

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38
Q

demonstration to show photoelectric emission. what do low frequencies result in?

A

no electrons, the deflection remains constat

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39
Q

below what number is there no loss in deflection

A

the threshold frequency

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40
Q

graph of number of electrons emitted and frequency of incident light

A

straight line graph started at the x-axis and threshold frequency

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41
Q

graph of number of emitted electrons and frequency of incident light, what’s on x-axis

A

frequency of incident light

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42
Q

graph of number of emitted electrons and frequency of incident light, what’s on y-axis

A

number of emitted electrons

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43
Q

what does the kinetic energy of emmitted elecgrons due to photoelectric emisiion depend on?

A

the frequency of the incident light (Hz)

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44
Q

to show the effect of intensity of incident light experiment. describe the set-up

A

a wire anode and cathode in a photocell (vacuum inside) connected to a milliammeter. bulb connect to battery and rheostat shining on anode

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45
Q

to show the effect of intensity of incident light experiment. the brighter the light

A

the more current recorded

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46
Q

to show the effect of intensity of incident light experiment. the number of electrons emitted is proportion to

A

the intensity of the incident light

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47
Q

rheostat

A

variable resistor

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48
Q

to show the effect of intensity of incident light experiment how can you vary the amount of light

A

the rheostst

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49
Q

what do you measure photocurrent with

A

an ammeter

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50
Q

to show the effect of intensity of incident light experiment. graph x-axis

A

photocurrent (mA)

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51
Q

to show the effect of intensity of incident light experiment. graph y-axis

A

intensity of incident light

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52
Q

to show the effect of intensity of incident light experiment describe the graph

A

straight line through the origin

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53
Q

what is photocurrent an indication of?

A

the number of emitted electrons

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54
Q

if you wanted to be very precise what could you use to measure the intensity of light

A

light meters

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55
Q

to show the effect of intensity of incident light experiment. the brighter the light

A

the more current recorded

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56
Q

to show the effect of intensity of incident light experiment. the number of electrons emitted is proportion to

A

the intensity of the incident light

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57
Q

rheostat

A

variable resistor

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58
Q

to show the effect of intensity of incident light experiment how can you vary the amount of light

A

the rheostst

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59
Q

what do you measure photocurrent with

A

an ammeter

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60
Q

to show the effect of intensity of incident light experiment. graph x-axis

A

photocurrent (mA)

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61
Q

to show the effect of intensity of incident light experiment. graph y-axis

A

intensity of incident light

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62
Q

to show the effect of intensity of incident light experiment describe the graph

A

straight line through the origin

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63
Q

what is photocurrent an indication of?

A

the number of emitted electrons

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64
Q

to show the effect of intensity of incident light experiment. describe the set-up

A

a wire anode and cathode in a photocell (vacuum inside) connected to a milliammeter. bulb connect to battery and rheostat shining on anode

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65
Q

to show the effect of intensity of incident light experiment. the brighter the light

A

the more current recorded

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66
Q

to show the effect of intensity of incident light experiment. the number of electrons emitted is proportion to

A

the intensity of the incident light

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67
Q

2 things that happens to the energy acquired by the electron

A

used to escape from the metal surface and the rest is used as kinetic energy

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68
Q

what does the number of electrons emitted depend on?

A

the number of photons ie. the intensity of the incident light

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69
Q

energy of incident photon =

A

work function + max. kinetic energy of emitted electron

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70
Q

to show the effect of intensity of incident light experiment. graph x-axis

A

photocurrent (mA)

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71
Q

to show the effect of intensity of incident light experiment. graph y-axis

A

intensity of incident light

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72
Q

to show the effect of intensity of incident light experiment describe the graph

A

straight line through the origin

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73
Q

what is photocurrent an indication of?

A

the number of emitted electrons

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74
Q

what did planck propose?

A

that electromagnetic radiation consisted of discrete quantities of energy called a quantum or a photon

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75
Q

what year did planck make his proposal

A

1902

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76
Q

what was the classical idea of electromagnetic radiation

A

that it was a continuous wave

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77
Q

energy of the quantum is proportional to

A

the frequency of the radiation

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78
Q

E =

A

hf

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79
Q

E

A

energy of the photon

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80
Q

photoelectric emission experiment: why does the leaf not collapse when zinc covered by a piece of glass

A

uv light cannot pass through ordinary glass and photoelectric emission does not occurs

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81
Q

f

A

frequency of the radiation

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82
Q

when a photon collides with an electron at or just within the surface of a metal

A

it may transfer its energy to the electron

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83
Q

3 applications of photoelectric effect

A

burglar alarms
smoke alarms
reading barcodes

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84
Q

what does it mean to be an all or none process

A

either the electron gets all the energy of the photon or none at all

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85
Q

energy of the photon is proportional to what

A

the frequency of radiation

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86
Q

2 things that happens to the energy acquired by the electron

A

used to escape from the metal surface and the

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87
Q

what did planck propose?

A

that electromagnetic radiation consisted of discrete quantities of energy called a quantum or a photon

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88
Q

what year did planck make his proposal

A

1902

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89
Q

what was the classical idea of electromagnetic radiation

A

that it was a continuous wave

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90
Q

energy of the quantum is proportional to

A

the frequency of the radiation

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91
Q

what can x-rays also have to help the cooling process

A

A liquid cooling system

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92
Q

E

A

energy of the photon

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93
Q

h

A

planck’s constant

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94
Q

f

A

frequency of the radiation

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95
Q

when a photon collides with an electron at or just within the surface of a metal

A

it may transfer its energy to the electron

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96
Q

what type of process is the transfer of energy

A

an all or none process

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97
Q

what does it mean to be an all or none process

A

either the electron gets all the energy of the photon or none at all

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98
Q

energy of the photon is proportional to what

A

the frequency of radiation

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99
Q

2 things that happens to the energy acquired by the electron

A

used to escape from the metal surface and the rest is used as

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100
Q

why is it good that there isn’t much gas inside the glass in the x-ray

A

electrons are less probable to hit a gas atom on the way

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101
Q

Φ

A

work function

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102
Q

threshold frequency is related to

A

work function (Φ)

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103
Q

threshold frequency equation

A

Φ = h fo

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104
Q

fo

A

threshold frequency

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105
Q

other way of writing hf, when equal to

Φ + 1/2 m v squared

A

hc
—— = Φ + 1/2 m v squared
λ

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106
Q

unit of energy in atomic physics

A

the electron volt

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107
Q

1 ev =

A

1.6 x 10 -19 joules

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108
Q

can you use electron volts in calculations

A

no, must convert to joules

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109
Q

photoelectric emission experiment: why does the leaf collapse when it is a negatively charged piece of metal

A

the uv light causes photoelectric emissions, ie electrons leave the surface of the metal, therefore the negative charge reduces and it collapses

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110
Q

photoelectric emission experiment: why does the leaf not collapse when the zinc is illuminated with green light

A

the frequency of the green light is lower than that of uv radiation and it is below the threshold frequency of zinc and photoemission cannot occur

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111
Q

photoelectric emission experiment: why does the leaf not collapse when the electroscope is charged positively

A

electrons emitted will be attracted back to the zinc plate, and if they could escape it would become even more positive and it would diverge more

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112
Q

3 applications of photoelectric effect

A

burglar alarms
smoke alarms
reading barcodes

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113
Q

3 steps in how x-rays are made

A

electrons emitted from the cathode by thermionic effect
accelerated to very high speed by high voltage
they hit the tungsten target and electrons are emitted

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114
Q

what does a lead shield do when making x - rays

A

protects the user from the harmful effect of x - rays

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115
Q

atomic view; 3 steps to making an x - ray

A
  • high speed electrons hit the tungsten anode and some are energetic enough to penetrate
  • outer electro falls into a lower energy level due to missing electron
  • excess energy emitted as a photon - an x - ray
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116
Q

99% of energy of the electrons

A

becomes heat energy when hits the tungsten

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117
Q

does tungsten melt

A

no, has a high melting point

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118
Q

what conducts the heat to the outside when making x - rays

A

the tungsten is set in copper which conducts the heat to the cooling fins outside

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119
Q

why does the heat escape off the fins into the air

A

the cooling fins have a large surface area

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120
Q

what can x-rays also have to help the cooling process

A

A liquid cooling system

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121
Q

who and when was the x-ray discovered

A

1895 by the German Physicist, W Rontgen

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122
Q

what does the intensity of an x-ray beam refer to?

A

the number of x-rays in the beam

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123
Q

what does the number of x-rays required depend on?

A

the surface area of what is to be examined

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124
Q

intensity depends on (3)

A

number of electrons crossing the tube
this depends on temperature of the heating coil
this depends on the current from the low voltage battery

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125
Q

what does the penetrating power of the x-rays refer to?

A

the ability of the x-rays to pass through different thicknesses of material or different densities of material

126
Q

penetrating power of x-rays depends on what (2)

A

speed of electrons crossing the tube

which depends on the value of high voltage

127
Q

2 uses of x-rays

A

damaged tissue in lungs is more dense, absorbs more x-rays, and shows up as a dense could on x-ray
can locate flaws in metal eg.crack in the body of an airplane

128
Q

what’s special about the gas in the x-ray tube

A

very low pressure inside, very little gas inside

129
Q

why is it good that there isn’t much gas inside the glass in the x-ray

A

electrons are less probable to hit a gas atom on the way

130
Q

what would gas molecule collisions do to the electrons

A

would slow them down

131
Q

relationship between x-rays and photoelectric emission

A

it is said that one is the reverse of the other

132
Q

what goes into making x-rays

A

electrons

133
Q

what goes out of making x-rays

A

photons

134
Q

when electrons hit the tungsten target when making x-rays

A

photons are emitted

135
Q

photoelectric effect what goes in

A

photon

136
Q

photoelectric effect what comes out

A

electrons

137
Q

photoelectric effect, what happens when photons fall on a metal

A

electrons emitted

138
Q

speed of a photon

A

c, speed of light

139
Q

we assume that all energy

A

is given to the electron (even though it isn’t)

140
Q

speed of an x-ray

A

same as speed of light when it’s in a vacuum

141
Q

what does it mean that x-rays are regarded as ionising radiation

A

they ionise the molecules of a material that they pass through

142
Q

are x-rays deflected in electric or magnetic fields

A

no

143
Q

what does it mean that x-rays aren’t deflected in electric or magnetic fields

A

they are neutral

144
Q

how are x-ray photographs possible

A

they cause a chemical reaction with they film in a similar way that light does

145
Q

1 danger of x-rays

A

excessive doses of x-rays could lead to certain forms of cancer

146
Q

what is a photon

A

a discrete quantity of electromagnetic radiation

147
Q

what is an x-ray

A

a photon of electromagnetic radiation of a very high frequency

148
Q

who discovered radioactivity

A

Becquerel

149
Q

when did Becquerel discover radioactivity?

A

1896

150
Q

intensity of radiation

A

number of emissions per second

151
Q

the intensity of radiation is proportional to

A

the mass of the radioactive sample

152
Q

3 types of radiation

A

alpha
beta
gamma

153
Q

emission of radiation

A

spontaneous

cannot be controlled

154
Q

definition of radioactivity

A

the spontaneous disintegration of the unstable nucleus of the unstable nucleus of an atom with he emission of a B or y radiation

155
Q

alpha charge

A

positively charged

156
Q

beta charge

A

negatively charged

157
Q

gamma charge

A

neutral, no charge

158
Q

alpha

A

a

159
Q

beta

A

B

160
Q

gamma

A

y

161
Q

what does the radiation do to the substance it passes through

A

it ionises it

splits it into positive and negative ions

162
Q

are all molecules encountered ionised

A

no

not all

163
Q

what happens to the ray or particle after each ionisation

A

it loses me kinetic energy

164
Q

how far does a good ioniser travel

A

not far

165
Q

how far does a bad ioniser travel

A

ver far

166
Q

how are penetration and ionisation related

A

penetration and ionisation are inversely proportional

167
Q

a is a

A

particle

168
Q

B is a

A

particle

169
Q

y is a

A

ray

170
Q

ionisation of a

A

very good ionising power

171
Q

penetration of a

A

very little penetration

172
Q

how do u stop an alpha particle

A

a thick sheet of paper

173
Q

how far do alpha particles travel

A

only a few centimetres in air

174
Q

ionisation of B

A

much less ionising than a particles

175
Q

penetration of B particle

A

100 times more penetrating power than a particles

176
Q

what can B particles pass through

A

up to 5mm thickness of aluminium

177
Q

ionisation of y rays

A

very little ionisation

178
Q

penetrating power of y rays

A

very penetrating

179
Q

what does it take to stop y rays

A

several cm of lead

180
Q

what do alpha particles consists of?

A

2 protons and 2 neutrons

181
Q

what is the alpha particle like

A

the nucleus of a helium atom

182
Q

what does a beta particle consist of?

A

an electron

183
Q

how is a beta particle formed?

A

a fast moving electron that comes from the nucleus of an atom
a neutron decays into a proton and an electrons and the electron is the B-particle

184
Q

symbol for a particle

A

4
He
2

185
Q

charge on an alpha particle

A

++

186
Q

symbol for a B particle

A

0
B
-1

187
Q

what is a gamma ray

A

a photon of electromagnetic radiation from the nucleus of an atom

188
Q

how do you calculate how many a and B particles

A
  • take the smaller atomic mass away from the larger atomic mass and divide by 4
  • that’s how many alpha particles
  • if it is lower than the atomic number still after taking away the 2 protons per a particle. that’s how many B particles were emitted
189
Q

how does the atomic number get bigger when you take away B particles

A

misusing a minus

190
Q

how do you construct a radioactive decay series

A

you put a new element in after you take away each alpha or beta particle

191
Q

how do you demonstrate ionisation

A 
charge a gold leaf electroscope 
bring a radioactive source near
it ionises the air above it
some ions attracted to cap
neutralised
less deflection
192
Q

demonstration to show penetration

A

bring the radioactive source near the geiger muller tube, you will notice an increase in count rate

193
Q

distance for a particle count to drop

A

10cm

194
Q

what to put between a particles and g m t for count to drop

A

a piece of paper

195
Q

what happens when you take the b radiation source away

A

no difference

196
Q

what to put between B particles and g m t for count to drop and why

A

sheets of aluminium. B particles cannot penetrate aluminium

197
Q

what to put between y rays and g m t for count to drop

A

a few cm thick lead

198
Q

who first performed Rutherford’s experiment?

A

Geiger and Mardsen

199
Q

what is the set up of Rutherford’s experiment?

A

a particles bombard a very thin piece of gold foil

200
Q

most a particles in Rutherford’s experiment?

A

go straight through gold foil

201
Q

some a particles in Rutherford’s experiment?

A

deflected through a small angle

202
Q

very few a particles in Rutherford’s experiment?

A

deflected through angles greater than 90º

203
Q

where was Rutherford’s experiment performed and why

A

in a vacuum because a particles have a very short range in air

204
Q

what detected the alpha particles?

A

a fluorescent screen

205
Q

how did the fluorescent screen detect the alpha particles

A

they cause scintillations

206
Q

what are scintillations

A

small flashes of light

207
Q

why would an a particle be deflected through a small angle

A

if it is repulsed by the positively charged nucleus

208
Q

why would an a particle be deflected through an angle greater than 90º

A

if the a particle was hiding straight for the nucleus

209
Q

why is there a very small chance of being deflected through an angle greater than 90º

A

the nucleus is very small, very small probability of going straight for it

210
Q

3 conclusions of Rutherford’s experiment

A
  • the nucleus is very small
  • electrons orbit the central nucleus
  • atom is mostly made of empty space
211
Q

4 features of the Bohr model of the atom

A
  • electrons only move in allowed orbits
  • when electrons move to a higher energy level, the atom is in an excited state
  • when the electron returns to its original position it emits a photon
  • energy emitted by an electron:
    hf = E1-E2
212
Q

what acts as the cathode in the geiger muller tube

A

a metal cylinder

213
Q

what acts as the anode in a geiger muller tube

A

a thin wire along the centre

214
Q

what does the voltage applied across the geiger muller tube depend on? 2

A

the density and pressure of the gas in the tube

215
Q

what is usually the gas in the geiger muller tube

A

argon

216
Q

what is in the geiger muller tube as well as argon?

A

a small amount of bromine

217
Q

function of bromine in geiger muller tube

A

a quenching agent

218
Q

how does the particle or ray enter the geiger muller tube

A

through a micra end window

219
Q

what happens as the particle or ray enters the geiger muller tube

A

it ionises an argon gas molecule

220
Q

what does the amount of molecules ionised depend on?

A

depends on the radiation

221
Q

what happens to the negative ions in a geiger muller tube

A

they are rapidly accelerated towards the wire anode

222
Q

what causes further ionisation in a geiger muller tube

A

high speed electrons

223
Q

what is it called when high speed electrons causes further ionisation in a geiger muller tube 2

A

gas amplication or avalanche

224
Q

in an avalanche, one electron can make how many electrons?

A

1 x 10 o the power of 8

225
Q

when the very large number of electrons in the geiger muller tube, reach the anode what happens

A

they pass through the external circuit as a fairly sizeable current

226
Q

what happens each time a current flows through a resistor

A

a potential drop occurs

227
Q

what counts the potential drops in a geiger muller tube

A

a counter (scaler or ratemeter)

228
Q

what can the counter in a geiger muller tube

A

can count the number of particles that enter the tube

229
Q

what is there a risk of when positive ions hit the cathode of a geiger muller tube and why is that bad

A

risk of electrons being knocked off the cathode and would register as a count on the scaler

230
Q

what does bromine do in a geiger muller tube

A

stops the electrons being emitted (quenching agent )

231
Q

what does a scaler give

A

total number of particles that entered the tube

232
Q

what does a ratemeter give

A

reading in counts per second

233
Q

law of radioactive decay

A

the rate of decay of a radioactive isotope is proportional to the number of atoms of the isotope present

234
Q

A is proportional to

A

N

235
Q

A =

A

λN

236
Q

N

A

number of atoms present in the sample

237
Q

λ

A

the decay constant

238
Q

unit of the decay constant

A

s to the minus one

239
Q

half life

A

the time required for half the nuclei in a radioactive sample to decay

240
Q

symbol of half life

A

T and a small half beside it

241
Q

unit of half-life

A

second (s)

242
Q

connection between decaying constant and the half life

A

1 ln2
T - = —–
2 λ

243
Q

if they give half life in hours for a maths question?

A

get seconds by dividing by 60x60

244
Q

if they want you to find amount left after a certain time but they give you the decaying constant?

A

find the half life first and then count out the hours

245
Q

if they give the half life in years

A

divide by 365x25x60x60

246
Q

how do you writ an equating to represent the decay of an isotope

A

original element -> B/a partices + new element

247
Q

rate of decay unit

A

bequerel

Bq

248
Q

1 bequerel =

A

1 second

249
Q

nuclear fusion definition

A

the combining of two small nuclei to form a larger nucleus with a loss in mass and a release in energy

250
Q

does nuclear fusion involve atoms and why

A

no because that would be chemical bonding. its nuclei

251
Q

example of nuclear fusion
2 2
H + H —>
1 1

A

4
He + energy
2

252
Q

2
H is also known as
1

A

deuterium

253
Q

deuterium is an

A

isotope of hydrogen

254
Q

2 problems with nuclear fusion

A

nuclei have positive charges and it is difficult to overcome the force of repulsion between them
controlling such high temperatures has not yet been achieved

255
Q

whats the speed problem with nuclear fusion

A

the very high speeds would require very high temperature, as hot as the sun

256
Q

what is a hydrogen bomb

A

a fusion reaction that has gone out of control

257
Q

1 advantage of fusion

A

very little radioactive waste to dispose of

258
Q

what is the required fuel for fusion and why is it good

A

deuterium, can be extracted from water, there would be no fuel shortage

259
Q

E = (einstein)

A

mc squared

260
Q

m

A

change in mass

261
Q

c

A

speed of light

262
Q

c =

A

3 x 10 to the power of eight m/s

263
Q

definition of nuclear fission

A

a nucleus is bombarded with a neutron, it splits into two nuclei of approximately equal size, two or three neutrons are emitted and the resulting loss of mass is released as energy

264
Q

2 main isotopes in natural uranium

A

u 238 and u 235

265
Q

percentage of u 238 in natural uranium

A

99.3% of world supply

266
Q

percentage of u 235 in natural uranium

A

0.7% of world supply

267
Q

if you increase the percentage of u 235

A

you get enriched uranium

268
Q

chain reaction

A

where one fission reaction causes another reaction which causes another reaction and so on

269
Q

a fission reaction in uranium is likely to

A

be followed by another one

270
Q

when do chain reactions not occur

A

when the hydrogen escapes through the surface of the sample

271
Q

how do you achieve the escaping of electrons?

A

keeping the samle size below a certain size, the critical size

272
Q

in a nuclear reactor

A

a chain reaction happens but the reaction is controlled

273
Q

in a nuclear bomb

A

a chain reaction happens but it is purposely let go out of control

274
Q

2 isotopes used in nuclear bombs

A

u235 or plutonium

275
Q

in a nuclear reactor what are the fuel rods made of 2

A

natural uranium or enriched uranium

276
Q

in a nuclear reactor what is the moderator usually made of

A

grahite or heavy water

277
Q

heavy water

A

D2O

278
Q

function of the moderator in a nuclear reactor

A

the neutrons are travelling too fast, but the moderator slows them down to a suitable speed for further fission

279
Q

what are the control rods in a nuclear reactor made of 2

A

boron or cadmium

280
Q

what can the control rods do

A

absorb the emitted neutrons

281
Q

function of the control rods

A

prevent further fission and it getting out of control

282
Q

how do you regulate the energy output in a nuclear reactor

A

by raising and lowering the control rods

283
Q

what does the coolant do in a nuclear reactor

A

pumps carbon dioxide around the system that carries the heat to the heat exchange unit

284
Q

where does the coolant in a nuclear reactor absorb the heat from?

A

very high kinetic energy creates temperature rises in a nuclear reactor

285
Q

what happens in the heat exchange unit in a nuclear reactor

A

the heat carried by the CO2 gas is used to boil water

286
Q

what generates the electricity in the heat exchange unit in a nuclear reactor

A

steam from boiling water is used to turn a turbine which creates electricity

287
Q

what do conventional power stations do?

A

boil water to make steam using fossil fuels

288
Q

what is the purpose of the shielding in a nuclear reactor

A

a thick concrete safety shield gives protection from neutrons and gamma rays to the outside world

289
Q

impact on miners, mining for uranium

A

the workers are exposed to radiation from materials like radon which can cause lung cancer

290
Q

what can an accident at a nuclear reactor do

A

release radioactive chemicals into the atmosphere

291
Q

why do used nuclear rods have to be carefully stored

A

because they are radioactive

292
Q

3 uses of radioisotopes

A

medical imaging
food irradiation
smoke detectors

293
Q

explain how medical imaging is a use of radioisotopes

A

radioactive chemicals with very short half lives are inserted into the body to trace blood flow or to help obtain an image of a particular organ

294
Q

explain how medical therapy is a use of radioisotopes

A

radiation from certain radioactive chemicals can be used to kill cancerous cells

295
Q

explain how food irradiation is a use of radioisotopes

A

if food is placed in a sealed container and bombarded with radiation , any harmful bacteria is killed and it stays fresh for a very long time

296
Q

explain how agriculture is a use of radioisotopes

A

the passage of chemicals through a plant can be traced by making the chemicals radioactive beforehand

297
Q

explain how radiocarbon dating is a use of radioisotopes

A

by examining the amount of C-14 in old samples of dead matter, their age can be determined

298
Q

explain how smoke detectors are a use of radioisotopes

A

they contain radioactive material that ionises the gap between the two electrodes, allowing current to flow. if smoke gets between it cuts it off and triggers the alarm

299
Q

explain how industry has a use of radioisotopes

A

manufacturing of paper: thickness can be checked

leaks in underground pipes can be detected

300
Q

4 factors that the harmful effects of radiation of on the human body depend on

A

nature of the radiation
the part of the body being exposed
how active the radioactive material is
the dose that the body reiceves

301
Q

a particle source outside the body

A

no damage, cannot penetrate skin

302
Q

B particle on the body

A

most radiation absorbed by surface tissue, a few mm of aluminium could protect you

303
Q

y rays on body

A

present greatest external radiation as they can penetrate deep into the body

304
Q

3 most susceptible parts of the body to harm by radiation

A

reproductive organs, blood forming organs eg. liver, and eyes to a smaller extent

305
Q

less vulnerable organs 4

A

hands, forearms, feet and ankles

306
Q

cosmic radiation

A

from outerspace, bombards the earth and we are constantly exposed to it

307
Q

what rock gives off radiation

A

granite has a minute traces of uranium which decays to radon gas

308
Q

2 things you can do to prevent radiation if your house is built above granite

A

proper ventilation so that the gas can escape and good insulation to stop gas entering

309
Q

how to measure background radiation

A

use a geiger muller counter and a ratemeter and take a count each minute for 20 minutes. it will vary a lot but get an average value

310
Q

4 ways to protect yourself from radiation

A

correctly dispose of radioactive waste
wear protective clothing (gloves, glasses)
do not eat or drink near radioactive material
measure radiation levels near you to ensure your safety

Physics (11 decks)

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