Properties of Radiation (Edexcel GCSE Combined Science) : Revision Note
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
Examiner Tips and Tricks
It is important to note that beta particles are only stopped by aluminium if it is a few mm thick. They can pass though aluminium which is thinner than this. This concept often comes up in exam questions.
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
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