Section 7 Flashcards

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1
Q

How can we detect ionising radiation?

A

Photographic film or a Geiger-Muller detector.

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2
Q

What are alpha particles?

A

Helium nuclei

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3
Q

What does emitting an alpha particle do to an atom?

A

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

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4
Q

What are beta particles?

A

Electrons

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5
Q

What do beta particles do to an atom when released?

A

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

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6
Q

What are gamma rays?

A

Very short wavelength EM waves.

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7
Q

How can alpha be blocked?

A

Paper, skin.

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8
Q

How can beta particles be stopped?

A

Thin metal.

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9
Q

How can gamma rays be stopped?

A

Thick lead or very thick concrete.

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10
Q

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

A

The less it will be deflected by the nucleus.

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11
Q

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

A

The more the alpha particle will be deflected.

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12
Q

What is a half life?

A

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

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13
Q

What makes beta and gamma suitable for medical tracers?

A

They will penetrate the skin and other body tissues.

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14
Q

Why is gamma used in industrial tracers?

A

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

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15
Q

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

A

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

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16
Q

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

A

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

17
Q

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

A

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

18
Q

How can you see how old an object is?

A

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.

19
Q

What can low doses of alpha cause?

A

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

20
Q

What do higher doses of alpha do?

A

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

21
Q

The harmful effects of alpha depend on what?

A

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

22
Q

How does radiotherapy work?

A

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

23
Q

How people who work with radioactive sources stay safe?

A

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

24
Q

What is nuclear fission?

A

The splitting of an atom, which releases energy.

25
Q

What happens when U-235 splits?

A

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

26
Q

What else is formed when the U-235 splits?

A

It forms two new daughter nuclei.

27
Q

What is the problem with the daughter nuclei?

A

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

28
Q

What does the moderator do?

A

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

29
Q

What do the control rods do?

A

Limit the rate of fission by absorbing excess neutrons.