Comparing Alpha, Beta & Gamma
- The properties of Alpha, Beta-plus, Beta-minus and Gamma are given in this table, and then described in more detail below
Different Properties of Nuclear Radiation
- The trend down the table shows:
- The range increases
- Penetrating power increases
- Ionisation decreases
Penetrating Power
- Alpha, beta and gamma have different properties
- They penetrate materials in different ways
- This means they are stopped by different materials
Alpha, beta and gamma are different in how they penetrate materials. Alpha is the least penetrating, and gamma is the most penetrating
- Alpha is stopped by paper, whereas beta and gamma pass through it
- Beta is stopped by a few millimetres of aluminium
- Gamma can pass through aluminium
- Gamma can be reduced by several metres of concrete or several centimetres of lead
- The more ionising a form of radiation is, the sooner it will react with the air it is moving through
- Strongly ionising radiation has the shortest range in air
- Alpha only travels a few centimetres in air
- Beta has a range of a few tens of centimetres
- Gamma is not absorbed by air and so has an infinite range, although it does become less intense with distance
Worked example
A student has an unknown radioactive source. They are trying to work which type of radiation is being given off:
A Alpha particles
B Beta particles
C Gamma rays
D Neutrons
They measure the count-rate, using a Geiger-Muller tube, when the source is placed behind different material. Their results are shown in the table below:
Which type of radiation is being given off by the source?
ANSWER: B
- The answer is not A because the radiation passed through the paper almost unchanged
- This means it is not alpha
- The answer is not C or D because the aluminium decreased the count-rate significantly
- This means it is not gamma (gamma penetrates aluminium)
- This also means it is not neutrons (neutrons penetrate aluminium, however you do not need to know this for your GCSE)
- Therefore, the source must be Beta particles
- The answer is not A because the radiation passed through the paper almost unchanged