P6 - Radioactivity

Question 1

Alpha (Type, symbol. what is it, equation symbol)

Answer 1

• A particle
• Symbol: α
• The nucleus of a helium atom:4
  He
  2

Question 2

Beta (Type, symbol. what is it, equation symbol)

Answer 2

• A particle
• Symbol: β
• A fast moving electron:0
  e
  -1

Question 3

Gamma (Type, symbol. what is it, equation symbol)

Answer 3

• An electromagnetic wave
• Symbol: γ
• A wave of the electromagnetic spectrum
• No equation symbol

Question 4

Neutron (Type, symbol. what is it, equation symbol)

Answer 4

• A particle
• Symbol: n1
  n
  0

Question 5

If nuclei don’t contain electrons, where do they come from?

Answer 5

• Neutrons are not stable, and so they decay make a proton and electron.
• This increases the atomic number, doesn’t change the mass number.

Question 6

Equipment used to detect radiation

Answer 6

• Geiger-Muller counter.
• It’s a small device that ‘clicks’ when radiation enters it.
• Each click is a tiny currently produced when radiation ionises the atoms of gas inside the tube.

Question 7

What stops an alpha particle?

Answer 7

• A few sheets of paper
• A few CM of air

Question 8

What stops a beta particle?

Answer 8

• A few mm of aluminium

Question 9

What stops a gamma wave?

Answer 9

• A few CM of lead
• A few M of concrete
• Some may still get through

Question 10

What does it mean for something to be ‘ionising’

Answer 10

It can remove electrons from atoms to produce positively charged ions.

Question 11

Half-life

Answer 11

• The time it takes for the activity of a radioactive material to halve.
  OR
• The time taken for half of the unstable nuclei in a sample to decay.

Question 12

What is contamination?

Answer 12

• When radioactive material is taken inside your body, or is on your skin.
• Internal contamination cannot be removed.

Question 13

What is irradiation?

Answer 13

• When there is radioactive material outside your body, but the radiation can travel into your body.

Question 14

What is irradiation?

Answer 14

• When there is radioactive material outside your body, but the radiation can travel into your body.

Question 15

What is taken into consideration before choosing a radioactive tracer?

Answer 15

Half life:
- If the half-life is too short, the tracer will decay before it can be detected (e.g. with gamma camera).
- If the half life is too long, then the tracer will continue to emit radiation for a longer duration, increasing the risk of cancer.

Question 16

Gamma knife

Answer 16

• A moveable source of gamma radiation, which focus gamma rays onto a cancer tumour.
• The source is moved around to reduce the radiation dose that healthy cells receive too.

Question 17

Describe nuclear fission

Answer 17

• A larger nucleus absorbs a neutron, then splits into two smaller daughter nuclei, which emit 2 or 3 neutrons.
• It’s a chain reaction (which is eventually stopped using stop rods)

Question 18

Describe nuclear fission

Answer 18

• Lighter nuclei join together to make a more stable nuclei in the process.
• This releases massive amounts of energy.
• Our sun uses this process (converts hydrogen nuclei into a helium nuclei)