P4 - Radiation For Life Flashcards Preview

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Flashcards in P4 - Radiation For Life Deck (310):
1

Which direction do electrons move when a polythene rod is rubbed with a duster?

From duster to rod

2

Which direction do electrons move when an acetate rod is rubbed with a duster?

From rod to duster

3

What is a static charge caused by?

Electrons moving

4

What happens if enough static charge builds up?

It can suddenly move which can cause sparks or shocks that may be dangerous.

5

How can a charged conductor be discharged safely?

By connecting it to earth with a metal strap (earthing).

6

How does earthing work?

Electrons flow down strap to ground if charge is negative and flow up strap from ground if positive.

7

What are ions?

Atoms or molecules with a charge

8

How does static attract dust?

Dust particles are charged and attract opposite charge. Objects in home are insulators (get easily charged) and attract dust.

9

How does static affect clothing?

When synthetic clothes dragged (head or other clothes) electrons scrape off, leaving static charge - two attract. Little sparks/shocks as charges rearrange themselves.

10

What causes shocks from door handles?

Walking on nylon carpet with insulating soles builds up charge. Touching metal door handle/water pipe allows charge to flow via conductor - little shock.

11

How can static on clothing become dangerous?

Charge may become large enough to make a spark - dangerous near inflammable gases or fuel fumes.

12

When can static become dangerous (other than on clothes)?

Fuel flowing out of pipe, paper drags on rollers or grain shoots out of pipe, static builds up. If too big, might spark - explosion in dusty/fumey places (petrol station).

13

What kind of places is static dangerous in?

Areas with inflammable liquids or a high concentration of oxygen (hospital operating theatre)

14

How do anti-static sprays work?

Make surface of a charged object conductive - provides an easy path for charges to move away.

15

How do insulating mats and shoes work?

Prevent static electricity moving through them - stops human getting shocked.

16

How do paint sprayers work?

Spray gun charged and object given opposite to attract. Paint drops repel each other (fine spray).

17

What is the good thing about electrostatic paint sprayers?

Method gives even coat and hardly any paint wasted. No shadows - everywhere covered.

18

How do dust precipitators work?

Smoke particles reach chimney bottom, meet wire grid/rods with high voltage and (-) charge. Dust particles gain electrons (become (-)) Dust particles induce charge on earthed metal plates Dust attracted to metal plates - stick forming larger particles When heavy enough, particles fall off/knocked off with hammer Falls and is removed

19

How does a defibrillator work?

2 paddles to power supply: Paddles firmly on chest (good electrical contact) and charged up Everyone moves away - operator holds insulated handles Charge passes through paddles to patient - heart contracts.

20

If you increase the voltage....

more current will flow

21

If you increase the resistance...

less current will flow (or more voltage is needed to keep same current flowing)

22

Current only flows when?

As long as there is a complete loop - broke circuit means no current.

23

What does the live wire do?

Carries voltage. Alternates between a high + and - voltage of about 230V

24

What colour is the live wire?

Brown

25

What does the earth wire do?

Works together with fuse for safety

26

What does the neutral wire do?

Completes tcircuit - electricity flows out through neutral - always at 0V.

27

What colour is the neutral wire?

Blue

28

What colour is the earth wire?

Green and yellow

29

What must all appliances with metal cases be?

earthed

30

What does double insulated mean?

If appliance has casing that is non-conductive (e.g. plastic) - doesn't need earthing (never live)

31

What happens is a fault develops where the live wire touches the metal case?

A big current flows through live wire. Surge blows fuse and causes wire inside to melt. Cuts off live supply by breaking circuit.

32

When the fuse blows, what does this prevent?

Electric shocks by isolating appliance. Stops flex overheating which may cause fire. Prevent further damage to appliance.

33

What is a circuit breaker?

Works like a fuse but can be reset and used again.

34

How should fuses be rated?

As near as possible but just higher than normal operating current.

35

What are the fixed fuse ratings?

3A, 5A and 13A

36

What is a variable resistor?

Rheostat - resistor whose resistance can be changed by turning a knob.

37

What are variable resistors good for?

Alternating the current flowing through a circuit. Turn up resistance, current drops (vice versa).

38

Why do thinner wires increase resistance?

Electric charge has less space to move through.

39

What is the resistance of a fixed resistor like?

Steady - at a constant temperature

40

How is resistance calculated?

Voltage / current

41

How is the ammeter set up in a circuit to measure resistance?

In series with other components

42

How is the voltmeter placed in a circuit to measure resistance?

In parallel around component being tested.

43

What is the official name for voltage around a test circuit?

Potential difference

44

What are compressions?

Parts of a wave under high pressure (lots of particles)

45

What are rarefactions in a wave?

Parts under low pressure (fewer particles)

46

What is wavelength?

A full cycle of a wave from crest to crest/compression to compression

47

What is frequency?

How many complete waves there are per second passing a certain point. Measured in hertz. Sound - high frequency=high pitch

48

What is amplitude?

Measured from rest position to crest. Tells you how much energy wave is carrying, or how loud it is.

49

How does a longitudinal wave move?

Vibrations are along same direction as wave is travelling

50

How does a transverse wave move?

Vibrations are at 90 degrees to direction of travel of the wave

51

What is ultrasound?

Electric devices can be made which produce electrical oscillations of any frequency. Easily converted into mechanical vibrations to produce longitudinal waves beyond range of human hearing.

52

How does ultrasound work when breaking down accumulation in the body?

Removing kidney stones. High energy of ultrasound at stone turns it into sand like particles. Particles pass out of body in urine. Doesn't need surgery and painless.

53

How does ultrasound work in body scanning?

Waves pass through body but are reflected back when they meet a boundary between two different media. Echoes are processed by computer to produce video image.

54

What advantages does ultrasound have?

Ultrasound is great for imaging soft tissue. Safer doesn't damage cells.

55

What do X-rays do compared to ultrasound?

Better for viewing bone. Can damage living cells by being ionising radiation, causing cancer at high doses.

56

What are radioactive materials made up of?

Atoms with unstable nuclei that naturally decay at random

57

What happens as radioactive material decays?

Give out alpha, beta and gamma. Nucleus often changes into new element.

58

What is the relative atomic mass number?

Top number = number of protons and neutrons (AKA mass number)

59

What is the atomic number?

Number of protons

60

What is an isotope?

Atoms of same element with different mass numbers

61

When does gamma radiation happen in decay?

After alpha and beta, if nucleus has extra energy to get rid of. Emits gamma ray that has no mass or charge - atomic and mass number don't change.

62

What is an alpha particle?

Helium nucleus of two protons and two neutrons

63

What charge does an alpha particle have?

+2

64

What mass does an alpha particle have?

4

65

What happens to the mass number when a nucleus emits an alpha particle?

Decreases by 4 because it loses 2 protons and 2 neutrons

66

What happens to the atomic number when the nucleus emits an alpha particle?

Decreases by 2 because it has 2 less protons

67

What is a beta particle?

Fast moving electron

68

What charge does a beta particle have?

-1

69

What mass does a beta particle have?

0

70

What happens to the mass number when a nucleus emits a beta particle?

Doesn't change - lost a neutron but gained a proton

71

What happens to the atomic number when a nucleus emits a beta particle?

Increases by 1 - has 1 more proton

72

What happens as more unstable nuclei decay?

Radioactivity of the source as whole decreases - older a resource, less radiation emitted.

73

What is the problem with trying to measure how quickly radioactive material decays?

Activity never reaches 0

74

What is the definition of half life?

Time taken for half of the radioactive nuclei now present to decay.

75

What does a short half life mean?

Activity falls quickly because lots of nuclei decay in a short time.

76

What does a long half life mean?

Activity falls slowly, because most of nuclei doesn't decay for a long time.

77

What causes ionisation?

When some materials absorb ionising radiation - can enter living cells and interact with molecules.

78

What does ionisation produce?

Charged particles called ions

79

What is nuclear radiation and X-rays types of?

Ionising radiation

80

What can X-rays and gamma rays do to electrons?

Transfer energy to electrons. Electrons then have enough energy to escape from atom, ionising it and leaving it positively charged.

81

What can beta particles do to electrons?

Remove electrons from atom/molecule leaving them positively charged.

82

What happens if a beta particle sticks to an atom?

Ionises it making it negatively charged.

83

What can alpha particles do to electrons in an atom?

Remove electrons, making atom positive.

84

Why are alpha particles good ionisers?

1. Relatively large - easy to collide with atoms or molecules 2. Highly charged - easily remove electrons from atoms they pass or collide with.

85

What do lower doses of ionising radiation tend to cause?

Minor damage without killing cells. Can give rise to mutant cells which divide uncontrollably - cancer.

86

What can high doses of ionising radiation tend to do?

Kill cells completely, which causes radiation sickness if a lot of cells all get blasted at once.

87

Which types of radiation are most dangerous outside the body?

Beta and gamma - can still get to delicate organs (pass through skin)

88

Why is alpha not dangerous outside the body?

It can't penetrate the skin

89

Which source of radiation is most dangerous inside the body?

Alpha - do all their damage in a localised area, highly ionising.

90

What sources of radiation are les dangerous inside the body?

Beta and gamma - less ionising, often pass straight out with very little damage

91

What level of frequency do X-rays and gamma rays have?

High frequency

92

What distance wavelength do X-rays and gamma rays have?

Short wavelength electromagnetic waves

93

How are gamma rays made?

Released from some unstable atomic nuclei when they decay. No way to control when they are released.

94

How are X-rays produced?

By firing high speed electrons at a heavy metal like tungsten. Much easier to control production of than gamma.

95

What can X-rays pass easily through?

Flesh

96

What can X-rays not pass easily through?

Thicker and denser material like bone or metal.

97

What makes an X-ray image?

Varying amount of radiation that's absorbed (denser materials absorb more X-rays)

98

How is gamma used to treat cancer?

*Gamma focused on tumour using wide beam. *Beam rotated round patient - tumour at centre. *Minimises exposure of normal cells to radiation, reducing risk of damage to rest of body.

99

What radiation can be used as medical tracers?

Radioactive isotopes that emit gamma (short half life - few hours)

100

How can a patient be given a medical tracer?

Injected, drunk, eaten or ingested.

101

How are medical tracers monitored?

Progress followed by radiation detector outside body.

102

What is an example of a medical tracer?

Iodine-123 absorbed by thyroid gland and shows if thyroid is taking all iodine it should.

103

Why must all isotopes in the body be beta or gamma?

Can penetrate tissue so are detectable outside. Can pass out easily.

104

How can medical instruments be sterilised?

Exposing them to high dose of gamma radiation.

105

Why does gamma radiation sterilise equipment?

It kills microbes

106

What is the advantage of using radiation instead of water to sterilise equipment?

Doesn't involve high temperatures. Plastic instruments can be sterilised without damaging them.

107

How can radiation be used as tracers in industry?

Tracks movement of waste material to find route underground of pipes or detect leaks/blockages

108

How is a leak detected using a radioactive tracer?

If detection of radioactivity stops/reduces must be a blockage/leak.

109

What must the isotope be for industrial tracers?

Gamma emitters so it can be detected through metal/pipe. Needs short half life.

110

Why does the industrial tracer need a short half life?

So it doesn't cause a hazard if it collects somewhere. Doesn't pollute water.

111

What source is used in a smoke detector?

A weak alpha source close to two electrodes.

112

How does a smoke alarm work?

In a fire, smoke particles are hit by alpha particles (less ionising of air) so current reduces, alarm sounds.

113

How does background radiation come from radioactivity of naturally occurring unstable isotopes?

All around us. In air, food, building materials and rocks. Large proportion of background radiation comes from natural sources.

114

How does background radiation come from space?

Known as cosmic rays. Come mostly from sun.

115

How does background radiation come from human activity?

E.g. Fallout from nuclear explosions, waste from industry and hospitals. Represents a small proportion of total.

116

How can the amount of background radiation vary?

Depending on where you are or job you have.

117

What 3 ways do we receive background radiation?

Naturally occurring unstable isotopes. Space. Human activity.

118

How can you work out the age of something using radioactive dating?

Measuring amount of radioactive isotope left in sample, and knowing its half life.

119

What fraction of the carbon in the air does carbon-14 make up?

1/10,000,000 (one ten-millionth)

120

What is the half life of carbon-14?

5730 years.

121

What happens when carbon-14 isotopes die?

Stop exchanging gas with air outside atmosphere and is trapped inside. Gradually decays.

122

How does uranium have a different half life?

Very long. Decay via series of short lived particles to produce stable isotopes of lead.

123

What is produced after 1 half life of uranium?

50% uranium 50% lead

124

What is produced after 2 half lives of uranium?

25% uranium 75% lead

125

What is the ratio of uranium to lead after 2 half lives?

1:3

126

What is the ratio of uranium to lead after 1 half life?

1:1

127

What is the ratio of uranium to lead before a half life?

1:0

128

What are nuclear power stations powered by?

Nuclear reactors

129

What happens in a nuclear reactor?

Controlled chain reaction takes place - nuclear fission.

130

What is nuclear fission?

Uranium/plutonium atoms split up - releasing energy as heat.

131

What happens after a nuclear reactor?

Heat from fission is used to produce steam. Steam turns turbines which drive generator, producing electricity.

132

What isotope is used in some nuclear reactors and bombs?

Uranium-235

133

What is uranium-235 like?

Quite stable

134

How do materials become radioactive?

When they absorb extra neutrons.

135

How is uranium-235 made radioactive?

By firing slow moving neutrons at the U-235 atom.

136

What does uranium-235 become to make it unstable?

Neutron joins, making it U-236 which is unstable.

137

What happens to the U-236?

Splits into 2 smaller nuclei, releasing energy and producing radioactive waste.

138

What does the split nucleus of U-236 also release?

2 or 3 fast moving neutrons which go on to produce a chain reaction.

139

What happens to neutrons from previous fission reactions of U-235?

They are used to hit other U-235 atoms

140

What is a nuclear bomb?

Chain reactions that are out of control.

141

How is the chain reaction controlled in nuclear reactors?

Using control rods

142

What are control rods usually made of?

Boron

143

What do control rods do?

Limit the rate of fission by absorbing excess neutrons.

144

What is nuclear fusion?

Two light nuclei combine to create a larger nucleus.

145

What is the equation for two hydrogen isotopes combining to form helium?

A image thumb
146

Where does all the energy released from stars come from?

Fusion at extremely high temperatures and pressures.

147

What is good about nuclear fusion?

Doesn't leave behind much radioactive waste and there is plenty of hydrogen available.

148

What is the big problem with nuclear fusion?

Only happens at really high pressures and temperatures (about 10,000,000 degrees C). No material can withstand that, so reactors are difficult to build. Safety issues.

149

Name an experimental fusion reactor...

JET (Joint European Torus)

150

Why are no fusion reactors producing electricity yet?

It takes more power to get up to temperature than reactor can produce.

151

Why is research into fusion being undertaken by international groups?

To share cost, expertise, experience and benefits (when problem solved)

152

What happens in a fusion bomb?

(AKA H-Bomb) Fission reaction creates high temperatures needed for fusion reaction which follows.

153

What does a new scientific theory have to go through before being accepted?

Validation Process

154

What is 'cold fusion'?

Nuclear fusion which occurs at room temperature.

155

Why is cold fusion not accepted?

Data was shared so experiments could be repeated. Very few managed to reproduce results reliably - not realistic method of energy production.

156

From duster to rod

Which direction do electrons move when a polythene rod is rubbed with a duster?

157

From rod to duster

Which direction do electrons move when an acetate rod is rubbed with a duster?

158

Electrons moving

What is a static charge caused by?

159

It can suddenly move which can cause sparks or shocks that may be dangerous.

What happens if enough static charge builds up?

160

By connecting it to earth with a metal strap (earthing).

How can a charged conductor be discharged safely?

161

Electrons flow down strap to ground if charge is negative and flow up strap from ground if positive.

How does earthing work?

162

Atoms or molecules with a charge

What are ions?

163

Dust particles are charged and attract opposite charge. Objects in home are insulators (get easily charged) and attract dust.

How does static attract dust?

164

When synthetic clothes dragged (head or other clothes) electrons scrape off, leaving static charge - two attract. Little sparks/shocks as charges rearrange themselves.

How does static affect clothing?

165

Walking on nylon carpet with insulating soles builds up charge. Touching metal door handle/water pipe allows charge to flow via conductor - little shock.

What causes shocks from door handles?

166

Charge may become large enough to make a spark - dangerous near inflammable gases or fuel fumes.

How can static on clothing become dangerous?

167

Fuel flowing out of pipe, paper drags on rollers or grain shoots out of pipe, static builds up. If too big, might spark - explosion in dusty/fumey places (petrol station).

When can static become dangerous (other than on clothes)?

168

Areas with inflammable liquids or a high concentration of oxygen (hospital operating theatre)

What kind of places is static dangerous in?

169

Make surface of a charged object conductive - provides an easy path for charges to move away.

How do anti-static sprays work?

170

Prevent static electricity moving through them - stops human getting shocked.

How do insulating mats and shoes work?

171

Spray gun charged and object given opposite to attract. Paint drops repel each other (fine spray).

How do paint sprayers work?

172

Method gives even coat and hardly any paint wasted. No shadows - everywhere covered.

What is the good thing about electrostatic paint sprayers?

173

Smoke particles reach chimney bottom, meet wire grid/rods with high voltage and (-) charge. Dust particles gain electrons (become (-)) Dust particles induce charge on earthed metal plates Dust attracted to metal plates - stick forming larger particles When heavy enough, particles fall off/knocked off with hammer Falls and is removed

How do dust precipitators work?

174

2 paddles to power supply: Paddles firmly on chest (good electrical contact) and charged up Everyone moves away - operator holds insulated handles Charge passes through paddles to patient - heart contracts.

How does a defibrillator work?

175

more current will flow

If you increase the voltage....

176

less current will flow (or more voltage is needed to keep same current flowing)

If you increase the resistance...

177

As long as there is a complete loop - broke circuit means no current.

Current only flows when?

178

Carries voltage. Alternates between a high + and - voltage of about 230V

What does the live wire do?

179

Brown

What colour is the live wire?

180

Works together with fuse for safety

What does the earth wire do?

181

Completes tcircuit - electricity flows out through neutral - always at 0V.

What does the neutral wire do?

182

Blue

What colour is the neutral wire?

183

Green and yellow

What colour is the earth wire?

184

earthed

What must all appliances with metal cases be?

185

If appliance has casing that is non-conductive (e.g. plastic) - doesn't need earthing (never live)

What does double insulated mean?

186

A big current flows through live wire. Surge blows fuse and causes wire inside to melt. Cuts off live supply by breaking circuit.

What happens is a fault develops where the live wire touches the metal case?

187

Electric shocks by isolating appliance. Stops flex overheating which may cause fire. Prevent further damage to appliance.

When the fuse blows, what does this prevent?

188

Works like a fuse but can be reset and used again.

What is a circuit breaker?

189

As near as possible but just higher than normal operating current.

How should fuses be rated?

190

3A, 5A and 13A

What are the fixed fuse ratings?

191

Rheostat - resistor whose resistance can be changed by turning a knob.

What is a variable resistor?

192

Alternating the current flowing through a circuit. Turn up resistance, current drops (vice versa).

What are variable resistors good for?

193

Electric charge has less space to move through.

Why do thinner wires increase resistance?

194

Steady - at a constant temperature

What is the resistance of a fixed resistor like?

195

Voltage / current

How is resistance calculated?

196

In series with other components

How is the ammeter set up in a circuit to measure resistance?

197

In parallel around component being tested.

How is the voltmeter placed in a circuit to measure resistance?

198

Potential difference

What is the official name for voltage around a test circuit?

199

Parts of a wave under high pressure (lots of particles)

What are compressions?

200

Parts under low pressure (fewer particles)

What are rarefactions in a wave?

201

A full cycle of a wave from crest to crest/compression to compression

What is wavelength?

202

How many complete waves there are per second passing a certain point. Measured in hertz. Sound - high frequency=high pitch

What is frequency?

203

Measured from rest position to crest. Tells you how much energy wave is carrying, or how loud it is.

What is amplitude?

204

Vibrations are along same direction as wave is travelling

How does a longitudinal wave move?

205

Vibrations are at 90 degrees to direction of travel of the wave

How does a transverse wave move?

206

Electric devices can be made which produce electrical oscillations of any frequency. Easily converted into mechanical vibrations to produce longitudinal waves beyond range of human hearing.

What is ultrasound?

207

Removing kidney stones. High energy of ultrasound at stone turns it into sand like particles. Particles pass out of body in urine. Doesn't need surgery and painless.

How does ultrasound work when breaking down accumulation in the body?

208

Waves pass through body but are reflected back when they meet a boundary between two different media. Echoes are processed by computer to produce video image.

How does ultrasound work in body scanning?

209

Ultrasound is great for imaging soft tissue. Safer doesn't damage cells.

What advantages does ultrasound have?

210

Better for viewing bone. Can damage living cells by being ionising radiation, causing cancer at high doses.

What do X-rays do compared to ultrasound?

211

Atoms with unstable nuclei that naturally decay at random

What are radioactive materials made up of?

212

Give out alpha, beta and gamma. Nucleus often changes into new element.

What happens as radioactive material decays?

213

Top number = number of protons and neutrons (AKA mass number)

What is the relative atomic mass number?

214

Number of protons

What is the atomic number?

215

Atoms of same element with different mass numbers

What is an isotope?

216

After alpha and beta, if nucleus has extra energy to get rid of. Emits gamma ray that has no mass or charge - atomic and mass number don't change.

When does gamma radiation happen in decay?

217

Helium nucleus of two protons and two neutrons

What is an alpha particle?

218

+2

What charge does an alpha particle have?

219

4

What mass does an alpha particle have?

220

Decreases by 4 because it loses 2 protons and 2 neutrons

What happens to the mass number when a nucleus emits an alpha particle?

221

Decreases by 2 because it has 2 less protons

What happens to the atomic number when the nucleus emits an alpha particle?

222

Fast moving electron

What is a beta particle?

223

-1

What charge does a beta particle have?

224

0

What mass does a beta particle have?

225

Doesn't change - lost a neutron but gained a proton

What happens to the mass number when a nucleus emits a beta particle?

226

Increases by 1 - has 1 more proton

What happens to the atomic number when a nucleus emits a beta particle?

227

Radioactivity of the source as whole decreases - older a resource, less radiation emitted.

What happens as more unstable nuclei decay?

228

Activity never reaches 0

What is the problem with trying to measure how quickly radioactive material decays?

229

Time taken for half of the radioactive nuclei now present to decay.

What is the definition of half life?

230

Activity falls quickly because lots of nuclei decay in a short time.

What does a short half life mean?

231

Activity falls slowly, because most of nuclei doesn't decay for a long time.

What does a long half life mean?

232

When some materials absorb ionising radiation - can enter living cells and interact with molecules.

What causes ionisation?

233

Charged particles called ions

What does ionisation produce?

234

Ionising radiation

What is nuclear radiation and X-rays types of?

235

Transfer energy to electrons. Electrons then have enough energy to escape from atom, ionising it and leaving it positively charged.

What can X-rays and gamma rays do to electrons?

236

Remove electrons from atom/molecule leaving them positively charged.

What can beta particles do to electrons?

237

Ionises it making it negatively charged.

What happens if a beta particle sticks to an atom?

238

Remove electrons, making atom positive.

What can alpha particles do to electrons in an atom?

239

1. Relatively large - easy to collide with atoms or molecules 2. Highly charged - easily remove electrons from atoms they pass or collide with.

Why are alpha particles good ionisers?

240

Minor damage without killing cells. Can give rise to mutant cells which divide uncontrollably - cancer.

What do lower doses of ionising radiation tend to cause?

241

Kill cells completely, which causes radiation sickness if a lot of cells all get blasted at once.

What can high doses of ionising radiation tend to do?

242

Beta and gamma - can still get to delicate organs (pass through skin)

Which types of radiation are most dangerous outside the body?

243

It can't penetrate the skin

Why is alpha not dangerous outside the body?

244

Alpha - do all their damage in a localised area, highly ionising.

Which source of radiation is most dangerous inside the body?

245

Beta and gamma - less ionising, often pass straight out with very little damage

What sources of radiation are les dangerous inside the body?

246

High frequency

What level of frequency do X-rays and gamma rays have?

247

Short wavelength electromagnetic waves

What distance wavelength do X-rays and gamma rays have?

248

Released from some unstable atomic nuclei when they decay. No way to control when they are released.

How are gamma rays made?

249

By firing high speed electrons at a heavy metal like tungsten. Much easier to control production of than gamma.

How are X-rays produced?

250

Flesh

What can X-rays pass easily through?

251

Thicker and denser material like bone or metal.

What can X-rays not pass easily through?

252

Varying amount of radiation that's absorbed (denser materials absorb more X-rays)

What makes an X-ray image?

253

*Gamma focused on tumour using wide beam. *Beam rotated round patient - tumour at centre. *Minimises exposure of normal cells to radiation, reducing risk of damage to rest of body.

How is gamma used to treat cancer?

254

Radioactive isotopes that emit gamma (short half life - few hours)

What radiation can be used as medical tracers?

255

Injected, drunk, eaten or ingested.

How can a patient be given a medical tracer?

256

Progress followed by radiation detector outside body.

How are medical tracers monitored?

257

Iodine-123 absorbed by thyroid gland and shows if thyroid is taking all iodine it should.

What is an example of a medical tracer?

258

Can penetrate tissue so are detectable outside. Can pass out easily.

Why must all isotopes in the body be beta or gamma?

259

Exposing them to high dose of gamma radiation.

How can medical instruments be sterilised?

260

It kills microbes

Why does gamma radiation sterilise equipment?

261

Doesn't involve high temperatures. Plastic instruments can be sterilised without damaging them.

What is the advantage of using radiation instead of water to sterilise equipment?

262

Tracks movement of waste material to find route underground of pipes or detect leaks/blockages

How can radiation be used as tracers in industry?

263

If detection of radioactivity stops/reduces must be a blockage/leak.

How is a leak detected using a radioactive tracer?

264

Gamma emitters so it can be detected through metal/pipe. Needs short half life.

What must the isotope be for industrial tracers?

265

So it doesn't cause a hazard if it collects somewhere. Doesn't pollute water.

Why does the industrial tracer need a short half life?

266

A weak alpha source close to two electrodes.

What source is used in a smoke detector?

267

In a fire, smoke particles are hit by alpha particles (less ionising of air) so current reduces, alarm sounds.

How does a smoke alarm work?

268

All around us. In air, food, building materials and rocks. Large proportion of background radiation comes from natural sources.

How does background radiation come from radioactivity of naturally occurring unstable isotopes?

269

Known as cosmic rays. Come mostly from sun.

How does background radiation come from space?

270

E.g. Fallout from nuclear explosions, waste from industry and hospitals. Represents a small proportion of total.

How does background radiation come from human activity?

271

Depending on where you are or job you have.

How can the amount of background radiation vary?

272

Naturally occurring unstable isotopes. Space. Human activity.

What 3 ways do we receive background radiation?

273

Measuring amount of radioactive isotope left in sample, and knowing its half life.

How can you work out the age of something using radioactive dating?

274

1/10,000,000 (one ten-millionth)

What fraction of the carbon in the air does carbon-14 make up?

275

5730 years.

What is the half life of carbon-14?

276

Stop exchanging gas with air outside atmosphere and is trapped inside. Gradually decays.

What happens when carbon-14 isotopes die?

277

Very long. Decay via series of short lived particles to produce stable isotopes of lead.

How does uranium have a different half life?

278

50% uranium 50% lead

What is produced after 1 half life of uranium?

279

25% uranium 75% lead

What is produced after 2 half lives of uranium?

280

1:3

What is the ratio of uranium to lead after 2 half lives?

281

1:1

What is the ratio of uranium to lead after 1 half life?

282

1:0

What is the ratio of uranium to lead before a half life?

283

Nuclear reactors

What are nuclear power stations powered by?

284

Controlled chain reaction takes place - nuclear fission.

What happens in a nuclear reactor?

285

Uranium/plutonium atoms split up - releasing energy as heat.

What is nuclear fission?

286

Heat from fission is used to produce steam. Steam turns turbines which drive generator, producing electricity.

What happens after a nuclear reactor?

287

Uranium-235

What isotope is used in some nuclear reactors and bombs?

288

Quite stable

What is uranium-235 like?

289

When they absorb extra neutrons.

How do materials become radioactive?

290

By firing slow moving neutrons at the U-235 atom.

How is uranium-235 made radioactive?

291

Neutron joins, making it U-236 which is unstable.

What does uranium-235 become to make it unstable?

292

Splits into 2 smaller nuclei, releasing energy and producing radioactive waste.

What happens to the U-236?

293

2 or 3 fast moving neutrons which go on to produce a chain reaction.

What does the split nucleus of U-236 also release?

294

They are used to hit other U-235 atoms

What happens to neutrons from previous fission reactions of U-235?

295

Chain reactions that are out of control.

What is a nuclear bomb?

296

Using control rods

How is the chain reaction controlled in nuclear reactors?

297

Boron

What are control rods usually made of?

298

Limit the rate of fission by absorbing excess neutrons.

What do control rods do?

299

Two light nuclei combine to create a larger nucleus.

What is nuclear fusion?

300

Q image thumb

What is the equation for two hydrogen isotopes combining to form helium?

301

Fusion at extremely high temperatures and pressures.

Where does all the energy released from stars come from?

302

Doesn't leave behind much radioactive waste and there is plenty of hydrogen available.

What is good about nuclear fusion?

303

Only happens at really high pressures and temperatures (about 10,000,000 degrees C). No material can withstand that, so reactors are difficult to build. Safety issues.

What is the big problem with nuclear fusion?

304

JET (Joint European Torus)

Name an experimental fusion reactor...

305

It takes more power to get up to temperature than reactor can produce.

Why are no fusion reactors producing electricity yet?

306

To share cost, expertise, experience and benefits (when problem solved)

Why is research into fusion being undertaken by international groups?

307

(AKA H-Bomb) Fission reaction creates high temperatures needed for fusion reaction which follows.

What happens in a fusion bomb?

308

Validation Process

What does a new scientific theory have to go through before being accepted?

309

Nuclear fusion which occurs at room temperature.

What is 'cold fusion'?

310

Data was shared so experiments could be repeated. Very few managed to reproduce results reliably - not realistic method of energy production.

Why is cold fusion not accepted?