Radioactivity

Question 1

What happens if a nucleus is unstable?

Answer 1

It decays and emits radiation (so is radioactive)

Question 2

What are the three kinds of radiation?

Answer 2

Alpha, beta and gamma

Question 3

Where are 4 ways background radiation is caused?

Answer 3

• From substances on earth e.g. building materials, rocks, soil
• Space (cosmic rays)
• Living things
• Human activity, like nuclear waste

Question 4

How does nuclear radiation cause ionisation?

Answer 4

By bashing into atoms, knocking electrons off them. Atoms (no charge) are turned into ions (charged)

Question 5

How can ionising radiation be detected?

Answer 5

With a Geiger-Muller detector or photographic film

Question 6

What are alpha particles made up of?

Answer 6

2 protons and 2 neutrons (Helium nuclei)

Question 7

What are the characteristics of an alpha particle? (size, speed, ionising, penetration, charge)

Answer 7

• Big, heavy and slow
• Strongly ionising
• Don’t penetrate far into materials
• Positively charged so deflected by electric and magnetic fields

Question 8

What are the characteristics of a beta particle? (size, speed, ionising, penetration, charge)

Answer 8

• Small and quite fast
• Moderately penetrating and ionising
• Negatively charged, so are deflected by electric and magnetic fields

Question 9

What are beta particles made up of?

Answer 9

Electrons

Question 10

What are the characteristics of a gamma ray? (size, speed, ionising, penetration, charge)

Answer 10

• Have no mass or charge, just energy
• Penetrate far into materials
• Weakly ionising, as they tend to pass through rather than collide with atoms

Question 11

What are alpha, beta and gamma particles stopped by?

Answer 11

Alpha - paper/skin/few cm of air
Beta - thin metal
Gamma - thick lead or concrete

Question 12

What does Rutherford’s model of the atom say? (mass, size, charge)

Answer 12

• Most of the mass must be concentrated in the centre, most of the atom it empty space since most particles pass through
• Nucleus must be small since very few alpha particles are deflected by much
• Positively charged as atoms can repel +vely charged alpha particles

Question 13

The faster the alpha particle is travelling, the ______ it will be deflected

Answer 13

Less

Question 14

The more positively charged a nucleus is, the _____ the alpha particle will be deflected

Answer 14

More

Question 15

The closer the alpha particle passes to the nucleus, the _____ it will be deflected

Answer 15

More

Question 16

What is half-life?

Answer 16

The time taken for half of the radioactive atoms now present to decay

Question 17

What is radioactivity measured in?

Answer 17

Becquerels

Question 18

What types of radiation do medical tracers use and why?

Answer 18

Beta or Gamma - they can penetrate skin and other body tissues

Question 19

What type of radiation do industrial tracers use and why?

Answer 19

Gamma - it’s not easily blocked (like alpha and beta)

Question 20

How is gamma radiation used to detect a leak in a pipe?

Answer 20

• Insert gamma source into pipe, let it flow along
• Go along the outside with a detector
• If there’s a leak, the gamma will collect outside the pipe –> extra high reading on radioactivity detector

Question 21

Which types of radiation are more hazardous when outside the body? and inside the body?

Answer 21

Outside - beta and gamma

Inside - alpha

Question 22

What can lower doses of radiation do to body cells?

Answer 22

Damage them, which causes mutations

Question 23

What can higher doses of radiation do to body cells?

Answer 23

Kills cells completely, causing radiation sickness if a large part of your body is affected at the same time

Question 24

What does the extent of the harmful effects of radiation depend on?

Answer 24

How much exposure you’ve had to the radiation, its energy and its penetration

Question 25

Which type of radiation is used to treat cancer?

Answer 25

Gamma

Question 26

How is low-level radioactive waste disposed of safely?

Answer 26

Buried in secure landfill sites

Question 27

How is high-level radioactive waste disposed safely of?

Answer 27

Put in glass blocks, inside metal canisters and buried deep underground somewhere that is geologically stable

Question 28

What precautions must you take when working with radioactive materials?

Answer 28

• No skin contact, hold with tongs at arm’s length
• Point source away from body
• Store in a sealed lead box
• Wear lead aprons/screens

Question 29

What is nuclear fission?

Answer 29

The splitting of an atom, which releases energy (nuclear power)

Question 30

When does a nucleus (eg U-235) split in nuclear fission?

Answer 30

When it absorbs a slow-moving neutron

Question 31

What is formed when U-235 splits in two?

Answer 31

Two daughter nuclei

Question 32

What is the main problem with nuclear power?

Answer 32

It produces huge amounts of radioactive waste which is difficult and expensive to dispose of safely

Question 33

In a nuclear reactor, what is the moderator made of and what does it do?

Answer 33

Usually made of graphite or water - slows neutrons so they can successfully collide with uranium nuclei and sustain the chain reaction

Question 34

What are the control rods made of and what do they do?

Answer 34

Boron - limit the rate of fission y absorbing excess neutrons

Question 35

What gas is pumped through the reactor and why?

Answer 35

Carbon dioxide - to carry away the heat generated

Question 36

What are the products of the fission of a uranium nuclei?

Answer 36

Thermal energy, nuclei, neutrons