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Physics GCSE > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What is an isotope?

A

Atoms of a particular element with the same number of protons but different numbers of neutrons

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2
Q

What happens when an electron absorbs EM radiation?

A

It moves from a lower to higher orbit

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3
Q

What happens when an electron emits EM radiation?

A

It moves from a higher to lower orbit

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4
Q

How can electrons leave an atom?

A
  • Absorbing enough EM radiation so they can escape the pull of the atom
  • Being hit by a particle such as an alpha or beta particle
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5
Q

When will unstable nuclei decay?

A

When alpha, beta, gamma or neutron radiation is emitted

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6
Q

How does an nucleus change when it undergoes alpha decay?

A

The mass number decreases by 4 and the proton number decreases by 2

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7
Q

How does an nucleus change when it undergoes beta+ decay?

A

The mass number stays the same but the proton number decreases by 1

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8
Q

How does an nucleus change when it undergoes beta- decay?

A

The mass number stays the same and the proton number increases by 1

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9
Q

In beta- decay, what decays?

A

A neutron into a proton and an electron

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10
Q

In beta+ decay, what decays?

A

A proton into a neutron and a positron

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11
Q

What are the properties of alpha radiation?

A
  • Very ionising
  • Stopped by a sheet of paper
  • Travels around 5cm in air
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12
Q

What are the properties of beta radiation?

A
  • Mildly ionising
  • Stopped by aluminium that is 3mm thick
  • Travels a few metres in air
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13
Q

What are the properties of gamma radiation?

A
  • Weakly ionising
  • Stopped by thick lead
  • Travels a few kilometres in air
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14
Q

What are the sources of background radiation?

A
  • Radon gas 50%
  • Ground and buildings 14%
  • Medical 14%
  • Nuclear power 0.3%
  • Cosmic rays 10%
  • Food and drink 11.5%
  • Other 0.2%
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15
Q

How can radiation be measured?

A

Using a Geiger-Müller tube

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16
Q

How can radiation be detected?

A

Using photographic film, if radiation is present the photographic film will darken

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17
Q

What is the ‘plum pudding model’?

A

A model of the atom where there are negatively charged ‘electron plumbs’ embedded in a positively charged ‘dough’

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18
Q

What was Rutherford’s model?

A

Rutherford’s model had a positively charged nucleus which the electrons orbited

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19
Q

What is the Bohr model?

A

Electrons orbit a positively charged nucleus, in well defined energy levels, he stated that they could move between energy levels if they gained or lost energy

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20
Q

What does the activity of a radioactive source measure?

A

The amount of atoms that decay every second

21
Q

What does the activity of a source depend on?

A

The amount of unstable atoms there are

22
Q

What is half-life?

A

Time it takes for half of the unstable atoms to decay

23
Q

What is activity measured in?

A

Becquerel (Bq)

24
Q

If a source has an activity of 240Bq what will it’s activity be after 2 half-lives?

A

240/2 = 120 120/2 = 60Bq

25
Q

What are the uses of gamma rays?

A
  • Kill cancer cells
  • Diagnose cancer
  • Preserve food
26
Q

What is the main use of alpha particles?

A

In smoke alarms

27
Q

What is the main use of beta particles?

A

To control the thickness of paper

28
Q

What is the danger of ionising radiation?

A

Ionising radiation causes atoms to turn into ions, these are very harmful to humans and can cause mutations which can lead to cancer

29
Q

What precautions can be taken when coming into contact with ionising radiation?

A
  • Limiting time of exposure
  • Wearing protective clothing
  • Increasing the distance between the person and the radioactive source
30
Q

What is irradiation?

A

Ionising radiation from an external radioactive source travelling to the body

31
Q

What is external contamination?

A

When radioactive materials come into contact with a person’s hair, skin, or clothing

32
Q

What is internal contamination?

A

When a radioactive source is eaten or drunk

33
Q

How do PET scanners work?

A
  • Patient given a radioactive tracer that decays quickly by emitting positrons
  • The positrons come into contact with electrons in the body, the two particles annihilate each other forming gamma rays
  • These gamma rays are detected by a PET scanner and processed by a computer to produce an image on a screen
  • The tracers need to be put into the body close to where they’re used as they decay quickly
34
Q

How are tumors treated using gamma rays?

A
  • Several beams of gamma rays are fired from different positions towards the cancer
  • Each beam damages the tumor but doesn’t kill it
  • Moving the beam ensures not too much ionising radiation comes into contact with the surrounding tissue
35
Q

How are tumors treated internally?

A
  • By injecting the radioisotope into the patient

- The patient eating or drinking something containing the radioisotope

36
Q

What are the different types of nuclear reactions that can be a source of energy?

A
  • Radioactive decay
  • Nuclear fission
  • Nuclear fusion
37
Q

What nuclear fusion?

A

The fusing of two smaller nuclei to form a larger nuclei, this is what happens in the sun

38
Q

What is nuclear fission?

A

When an unstable nuclei splits into two smaller ones resulting in huge amounts of energy being released

39
Q

Is nuclear power efficient?

A

Yes, but nuclear power stations produce radioactive nuclear waste which can stay radioactive for thousands of years

40
Q

What are the advantages of nuclear power?

A
  • Carbon dioxide isn’t produced so it doesn’t contribute to climate change
  • Supplies of nuclear fuels
41
Q

What are the disadvantages of nuclear power?

A
  • It’s expensive to store nuclear waste safely
  • If an accident in a nuclear power station happens it can spread radioactive material over a large area
  • Many people don’t want nuclear power stations to be built as they think that nuclear power is dangerous
42
Q

When does a uranium-235 nucleus split?

A

When it absorbs a neutron

43
Q

What does the fission of uranium-235 produce?

A

Two daughter nuclei and two or more neutrons

44
Q

When neutrons are released following nuclear fission, other nuclei may absorb them and undergo fission, what is this called?

A

A chain reaction

45
Q

How is electrical energy generated from power stations?

A
  • Fuel rods containing uranium undergo nuclear fission and thermal energy is released
  • Thermal energy is used to heat water and produce steam
  • The steam causes turbines to rotate which turn the generator so it generates electricity
  • The steam is cooled back into water in a cooler so it can be used again
  • Extra thermal energy is released by cooling towers or into the sea
46
Q

How are chain reactions controlled?

A

Using control rods that absorb neutrons

47
Q

Why is nuclear fusion not a suitable source of energy?

A

It can only occur at very high temperatures and pressures because of electrostatic repulsion happens normally

48
Q

Does nuclear fusion or fission happen in the sun?

A

Fusion, hydrogen nuclei are converted to helium nuclei

Physics GCSE (17 decks)

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