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Physics 🔭 > P6 Radioactivity > Flashcards

P6 Radioactivity Flashcards

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1
Q

What does it mean for an electron to become excited?

A

Move to a higher energy level

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2
Q

When can electrons in a gas become excited?

A

When the gas is heated / current is passed through it

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3
Q

After becoming excited electrons fall back down to their shell and lose energy. This is emitted as?

A

An electromagnetic wave in a random direction

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4
Q

The bigger the fall, the more…

A

Energy lost
Energetic EM wave emitted

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5
Q

Every element has different ____ levels. Therefore if there is an unknown gas we can ____ it and see which ___ it emits

A

Energy
Heat
Wavelengths

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6
Q

All EM waves except what can be emitted in this way?

A

Gamma

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7
Q

When light of all colours is shone through a cold gas, most wavelengths…

A

Go straight through

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8
Q

Electrons can only absorb light with…

A

Just the right energy to move them up to another energy shell

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9
Q

After electrons absorb light they’ll then fall back down, emitting…

A

An identical wavelength (colour) of light in a random direction

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10
Q

An electron can gain enough energy to ___ ___ from the atom. This is known as ____ and we say the atom has been ____

A

Break free
Ionisation
Ionised

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11
Q

Some isotopes contain too many ____, this makes them ___ and therefore radioactive. We call them _____

A

Neutrons
Unstable
Radioisotopes

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12
Q

Radioactive substances consist of unstable ___ which ___, emitting alpha / beta / gamma

A

Nuclei
Decay

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13
Q

What is an alpha particle?

A

Two protons and two neutrons
The same as a helium nucleus

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14
Q

A beta particle is?

A

A high energy electron

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15
Q

What is gamma?

A

An electromagnetic wave, high frequency, short wavelength

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16
Q

Absorbing what can make a material radioactive?

A

Neutrons

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17
Q

Losing a gamma ray has what effect on a nucleus?

A

The nucleus stays the same but has less energy

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18
Q

How is a beta particle formed?

A

A neutron turns into a proton + electron

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19
Q

Alpha is how ionising?

A

Highly

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20
Q

Beta is how ionising?

A

Moderately

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21
Q

Gamma is how ionising?

A

Weakly

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22
Q

Alpha is how penetrating?

A

Weakly

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23
Q

Beta is how penetrating?

A

Moderately

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24
Q

Gamma is how penetrating?

A

Highly

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25
Q

Alpha can be stopped by…

A

Paper
5cm of air

26
Q

Beta can be stopped by…

A

3-5mm of aluminium

27
Q

Gamma can be stopped by…

A

Thick lead
Metres of concrete

28
Q

Why is ionisation of living things potentially dangerous?

A

Ionisation within living cells can damage DNA —> cell mutation / death

29
Q

What is irradiation?

A

When the radiation from a material damages the cells. You can move away from the source and end the irradiation

30
Q

What is contamination?

A

If some of the radioactive material itself is swallowed or inhaled, it emits radiation inside the body, causing damage

31
Q

List the precautions your teacher took while handling radioactive sources

A

Wearing lab coat and gloves to avoid contamination
Tongs and source holder to increase distance between source + people
Experiment done quickly to limit time close to source
Pointed sources away from students

32
Q

What is background radiation?

A

Radiation all around us

33
Q

What is half-life?

A

The half-life of a radioactive element is the time it takes for half the nuclei in a sample to decay

34
Q

Carbon-__ is made in the upper atmosphere by ___ __ and decays elsewhere at the same rate

A

14
Neutron capture

35
Q

Living organisms take in ___ including some of the radioactive C-14

A

Carbon

36
Q

When organisms die they stop taking in C02 (plants) or ____ (animals) so the amount of C-14 in them starts _____ as it radioactively decays

A

Glucose
Decreasing

37
Q

C-14 has a half life of….

A

5730 years

38
Q

The ratio of C-14 to C-__ in living objects can be compared to the artefact and therefore it can be ___

A

12
Dated

39
Q

How is radioactivity used to treat cancer?

A

An x-ray or gamma source is rotated around patient’s body, aiming x-rays / gamma rays at tumour. This ensures the tumour gets large amount of radiation (hopefully cells die) while healthy cells receive lowest amount possible

40
Q

What radiations are emitted from medical tracers we use? Why?

A

Usually gamma - most penetrating, least ionising
Sometimes beta

41
Q

Why is alpha never used for medical tracers?

A

Would cause damage (most ionising) and wouldn’t be detected (least penetrating)

42
Q

How do we get medical tracers into patient?

A

Injection, ingestion, inhalation (3 Is)

43
Q

Radioactive iodine behaves the same as non-radioactive iodine. This is good because?

A

Our body won’t reject it

44
Q

An appropriate half-life for a medical tracer might be…

A

4-6 hours

45
Q

What is nuclear fission?

A

The process of splitting a heavy nucleus to form 2 or more small nuclei, releasing large quantities of energy

46
Q

What is a chain reaction?

A

A reaction where the product of the first reaction causes further reactions to take place

47
Q

A ___ moving neutron is absorbed by the nucleus of a ____-235 atom

A

Slow
Uranium

48
Q

The uranium nucleus splits into two smaller, still _____ nuclei, releasing ____ and ____

A

Radioactive
Heat
Gamma

49
Q

When the uranium nucleus splits, 2 or 3 ___ are also released; these could be ___ by other uranium nuclei causing further ____ reactions

A

Neutrons
Absorbed
Fission

50
Q

Advantages of nuclear power?

A

Produces no C02
Stores more energy per kg than any other fuel (4 million times more than coal)
Reliable, produces 24/7

51
Q

Disadvantages of nuclear power?

A

Generate nuclear waste that emit alpha, beta and gamma, and stay radioactive for millions of years - has to be treated, sealed and buried
Closing power station is expensive because some parts have become radioactive by absorbing neutrons
Nuclear accidents are rare but have serious consequences

52
Q

What is nuclear fusion?

A

The process of joining together two lighter nuclei to form one large nucleus, releasing large quantities of energy

53
Q

What happens if we bring two protons (hydrogen nuclei) together?

A

They repel

54
Q

In order to fuse, protons must move very fast. What must the temp of the substance be?

A

Extremely hot

55
Q

How do we increase the likelihood of successful collisions?

A

Increase pressure and density

56
Q

What does E= delta m c2 mean

A

Energy = change in mass x speed of light squared

57
Q

Energy and mass are…

A

Interchangeable

58
Q

If we can recreate nuclear fusion in a controlled way, we could produce energy that:

A

Produces no C02
Produces no long half-life waste
Is inherently safe - if something goes wrong the temp drops, and the reaction stops

59
Q

What is an absorption spectrum?

A

A continuous spectrum with dark lines where particular wavelengths / frequencies of EM waves have been absorbed

60
Q

Where does background radiation come from?

A

The air, rocks, the sun, space and artificial sources

61
Q

Define radioactive decay

A

A random process by which an unstable nucleus loses energy by emission of radiation or a particle

62
Q

What is an emission spectrum?

A

A set of wavelengths / frequencies of EM waves emitted by an atom when excited electrons move to lower energy levels

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