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Physics > P7: Radioactivity > Flashcards

P7: Radioactivity Flashcards

1
Q

What is radioactive decay

A

When an unstable nucleus will become more stable over time by spontaneously (random) emitting ionising radiation.

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2
Q

What are the names of substances that decay radioactively

A

Radioactive substances

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3
Q

What are the three types of ionising radiation

A

Alpha
Beta
Gamma

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4
Q

What is alpha radiation

A

A type of radiation produced by alpha decay.
It releases helium nuclei, known as alpha particles

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5
Q

What is beta radiation

A

Another type of radiation produced by beta decay. It releases electrons known as beta particles

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6
Q

What is gamma radiation

A

Final type of radiation produced by gamma decay. It is a high electromagnetic energy wave with higher frequencies than X Rays

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7
Q

What is an alpha particle

A

Helium nuclei

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8
Q

What is a beta particle

A

Electron

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9
Q

What is a fact about radioactive decay

A

Unpredictable
We cannot predict when atoms will emit ionising radiation

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10
Q

What are the three ways we can detect radioactivity

A

Cloud chambers
Photographic film
Geiger counter

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11
Q

What is a cloud chamber

A

Containers full of air containing alcohol vapour.

Ionising radiation enters the air and leaves a trail of ionised air molecules.

The alcohol vapour condenses on the ionised air molecules, showing the trail of radiation

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12
Q

What is the effect of the photographic film

A

Ionising radiation shares the same effect with this and light.
A bright spot appears wherever ionising radiation hits the film

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13
Q

What is a geiger counter

A

Ionising radiation enters a tube of low pressure gas. Atoms in the gas are ionised, knocking electrons out of the atom. Gases then conduct electricity and completes an electric circuit.

When radioactive substances enter a Geiger counter, it makes a clicking noise

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14
Q

What is background radiation

A

This is when atoms or isotopes are very common, they even exist in our body.

They decay radioactively, meaning we are always surrounded by background radiation

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15
Q

What is the count rate for geiger counters

A

Number of decays recorded per second

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16
Q

What are sources of background radiation

A

Foods
Radon gas
Rocks
Sun

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17
Q

What are the properties of an alpha particle

A

An alpha particle contains 2 protons and 2 neutrons.

This creates a relative mass of 4 for an alpha particle.

Alpha particles are big and heavy so alpha radiation is strongly ionising.

They do lots of damage, but can be stopped by small amounts of matter such as paper

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18
Q

What are the properties of a beta particle

A

A beta particle is made up of high energy electrons.

Beta radiation is more penetrating than gamma radiation but less ionising than alpha radiation.

It can pass through paper but is stopped by aluminium foil

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19
Q

What are the properties of gamma radiation

A

Gamma radiation is the least ionising of the three.

It does deal less damage than alpha and beta radiation and cannot be stopped by ANYTHING

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20
Q

How does penetration link to ionising radiation

A

Strongly ionising radiation is less likely to penetrate materials. It damages materials much more so it comes to a stop soon.

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21
Q

Out of the three types of radiation, which is the most penetrating and ionising

A

Gamma is the most penetrating

Alpha is the most ionising

22
Q

How can we test beta radiation

A

Paper production

Beta particles are able to be chucked through paper to observe whether the paper produced is the right thickness.

23
Q

What if the paper is too thick to detect beta radiation

A

Fewer beta particles reach the detector. Production is then stopped

24
Q

How can we test alpha radiation

A

Smoke detectors

A radioactive material fires alpha particles at a smoke detector.

25
Q

What happens if smoke comes in contact between the two objects

A

Less alpha particles will reach the detector, setting off the smoke alarm

26
Q

What are ways to test gamma radiation

A

Sterilisation: we can use gamma radiation to sterilise medical equipment in hospitals, which can kill bacteria and viruses

Internal organ exploration: If a gamma emitting isotope is put into a patient’s body, we can follow the radiation’s movement around the body. Due to being the most penetrating type, it can pass through objects more easily than beta and alpha radiation. This means gamma can leave the body without creating too much damage (ionisation).

Gamma radiation also has a short half life meaning radiation vanishes quickly

27
Q

What is nuclear fission

A

Nuclear fission splits 1 nucleus into 2 smaller nuclei, which normally takes place in nuclear reactors.

A neutron collides with a large nucleus and is absorbed. This forms an unstable nucleus.

The nucleus then splits into fragments. This releases large energy amounts and more neutrons. Neutrons can often collide with nuclei.

Energy released is then used to boil water, which rotates a turbine. The turbine then turns a generator, producing electricity

28
Q

What happens if nuclear fission isn’t controlled?

A

The rate of nuclear fission becomes faster and faster. This creates a chain reaction where each fission stage produces more and more energy. This can lead to an explosion

29
Q

What are atom bombs

A

Atom bombs use these chain reactions to create large explosions and emit lots of energy

30
Q

What is nuclear fusion

A

Nuclear fusion joins 2 smaller nuclei to create 1 large nucleus. Creating this large nucleus releases energy

31
Q

What are hydrogen bombs

A

Hydrogen bombs use nuclear fusion to release lots of energy in an explosion

32
Q

What do stars use to generate energy

A

Nuclear fusion

33
Q

What is the difference between nuclear fusion and nuclear fission

A

Nuclear fission: Imagine a raindrop splitting when coming across an object.

Nuclear fusion: Imagine two raindrops colliding to form a new larger raindrop

34
Q

What happens in alpha decay

A

In alpha decay, 4 nucleons (protons and neutrons combined) are lost in the form of an alpha particle. 2 protons are lost so the initial atom becomes a different element

35
Q

What happens in gamma decay

A

In gamma decay, 0 nucleons (protons and neutrons combined) are lost in a gamma ray. The element does not change when gamma rays are emitted

36
Q

What happens in beta decay

A

In beta decay, 1 electron is carried away. The number of nucleons (protons and neutrons combined) stays the same but nitrogen is formed from the original carbon.

37
Q

What is a nuclear fission equation

A

The number of protons remains the same but 4 nucleons (protons and neutrons combined) are released to continue a chain reaction with other atoms

38
Q

What happens during alpha, beta and gamma decay

A

An unstable nucleus becomes more stable

39
Q

Which isotope of uranium is used in nuclear fission

A

Uranium-235

40
Q

What is the product of beta decay of a carbon atom

A

A nitrogen ion and an electron

41
Q

What is half life

A

The average time taken for the number of radioactive nuclei to halve.

42
Q

What is the activity of radioactive substance measured in

A

Becquerels (Bq)

43
Q

What two adjectives describe half lives

A

Constant: half life for any isotope of an element is constant. The half life of unstable isotopes can be seconds or millions of years

Unpredictable: Half life for any isotope of an element is unpredictable, despite large amounts of nuclei behaving in predictable ways.

44
Q

How can we find the half life of an isotope from graphs or tables

A

Measure the time it takes for the radioactive count rate or the number of unstable nuclei to halve

45
Q

How do we work out substance radiation

A

Total radiation - Background radiation

46
Q

How can we calculate the half life of a radioactive isotope

A

Strip out the background radiation of the environment around us.

47
Q

What is the calculation to find out the level of radiation due to substance

A

Level of radiation with substance and background radiation - Level of background radiation

48
Q

What can we use to find out the level of background radiation

A

Geiger counters

49
Q

What damage can ionising radiation cause

A

Failed organs due to mutations that lead to cancer, and cell damage

50
Q

Half life question

An element has a half life of 5 years.

If there are 571g of the element in a substance, how much is left after 15 years?

A

After 15 years, the amount of the element will have been halved 3 times

15/5 = 3

So the amount left in the sample is

571 x 1/2 cubed = 71.375 g

51
Q

What are the safety precautions of ionising radiation damage

A

Reduced exposure
Storage
Usage
Handling

Physics (7 decks)

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