Section 7

Question 1

How can we detect ionising radiation?

Answer 1

Photographic film or a Geiger-Muller detector.

Question 2

What are alpha particles?

Answer 2

Helium nuclei

Question 3

What does emitting an alpha particle do to an atom?

Answer 3

Decrease the atomic number of the nucleus by 2 and the mass number by 4.

Question 4

What are beta particles?

Answer 4

Electrons

Question 5

What do beta particles do to an atom when released?

Answer 5

Increase the atomic number by 1 and the mass number remains the same.

Question 6

What are gamma rays?

Answer 6

Very short wavelength EM waves.

Question 7

How can alpha be blocked?

Answer 7

Paper, skin.

Question 8

How can beta particles be stopped?

Answer 8

Thin metal.

Question 9

How can gamma rays be stopped?

Answer 9

Thick lead or very thick concrete.

Question 10

When being shot through a substance what happens if the alpha particle is travelling fast?

Answer 10

The less it will be deflected by the nucleus.

Question 11

What will happen to an alpha particle if the nucleus is more positively charged?

Answer 11

The more the alpha particle will be deflected.

Question 12

What is a half life?

Answer 12

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

Question 13

What makes beta and gamma suitable for medical tracers?

Answer 13

They will penetrate the skin and other body tissues.

Question 14

Why is gamma used in industrial tracers?

Answer 14

So the radiation can be detected through any rocks or earth surrounding the pipe.

Question 15

Why does the gamma have to have a short life when being used in industrial tracers?

Answer 15

So not to cause a long-term hazard if it collects somewhere.

Question 16

How can gamma show if there is a crack in the pipe?

Answer 16

The gamma source will collect outside the pipe, where the crack is, and the detector will show extra high radioactivity at that point.

Question 17

In medical tracers why does the radioactive source need to have a short half-life?

Answer 17

So you can use less of the radioactive source but still get a reading on your detector.

Question 18

How can you see how old an object is?

Answer 18

By measuring the amount of radioactive isotope left in the sample, and knowing the half-life, you can work out how long the object has been around.

Question 19

What can low doses of alpha cause?

Answer 19

They don’t kill cells but can cause mutations in cells which then divide uncontrollably - this is cancer.

Question 20

What do higher doses of alpha do?

Answer 20

Tend to kill cells completely, causing radiation sickness if a large part of the body is affected at the same time.

Question 21

The harmful effects of alpha depend on what?

Answer 21

How much exposure you have to the radiation, its energy and penetration.

Question 22

How does radiotherapy work?

Answer 22

It involves a high dose of gamma rays and kills the cancer cells preventing them dividing.

Question 23

How people who work with radioactive sources stay safe?

Answer 23

Wear lead aprons, use remote-controlled robot arms when handling the sources.

Question 24

What is nuclear fission?

Answer 24

The splitting of an atom, which releases energy.

Question 25

What happens when U-235 splits?

Answer 25

Releases a small number of neutrons which go on to hit more U-235 nuclei, causing them to split and creating a chain reaction.

Question 26

What else is formed when the U-235 splits?

Answer 26

It forms two new daughter nuclei.

Question 27

What is the problem with the daughter nuclei?

Answer 27

They are radioactive and therefore huge amounts of radioactive waste is produced which is difficult and expensive to dispose of safely.

Question 28

What does the moderator do?

Answer 28

Slows neutrons so that they can successfully collide with uranium nuclei and sustain the chain reaction.

Question 29

What do the control rods do?

Answer 29

Limit the rate of fission by absorbing excess neutrons.