Uses of Radiation

Radiation is used in a number of different ways, for example:
- Producing electricity through nuclear fission
- Medical procedures including diagnosis and treatment
- Testing material
- Determining the age of ancient artefacts
- Checking the thickness of materials
- Smoke detectors
The properties of the different types of radiation determine which one is used in a particular application

Smoke Detectors & Alpha Particles

Alpha particles are used in smoke detectors
The alpha radiation will normally ionise the air within the detector, creating a current
The alpha emitter is blocked when smoke enters the detector
The alarm is triggered by a microchip when the sensor no longer detects alpha

Smoke alarm diagram 1, downloadable IGCSE & GCSE Physics revision notes Smoke alarm diagram 2, downloadable IGCSE & GCSE Physics revision notes

In the diagram on the right, alpha particles are stopped by the smoke, preventing the flow of current and triggering the alarm

Worked example

Explain why is alpha radiation used in smoke detectors, and not beta or gamma radiation.

Smoke Detector, downloadable AS & A Level Physics revision notes

- Consider the different properties of alpha, beta and gamma:
  - Alpha is the most weakly penetrating and strongest ioniser
  - Beta and gamma have stronger penetrating power and weaker ionising power
- If beta or gamma radiation were used in this situation then they would pass straight through the smoke and the alarm would not go off
- Therefore, since alpha is absorbed by smoke, and beta and gamma are not, this makes it most suitable for use in a smoke detector

Examiner Tip

You do not need to know the different uses of the different types of radiation but you must be able to use your knowledge of the properties of the different types in order to determine which source is the most appropriate for a particular use.

Students often find application questions quite intimidating. Application questions present you with an unfamiliar context, and you have to apply what you have learned about the physics to that specific situation.

There are 3 types of radiation to choose from: alpha, beta and gamma. The properties of each will either make them suitable or unsuitable for a particular job. If you get stuck on why a certain type of radiation is suitable, think about why the other types are not suitable. Why wouldn't you use alpha particles for determining the thickness of paper? Because alpha particles are stopped by paper, so the detector would detect nothing. Why wouldn't you use gamma radiation? Because all the gamma radiation will pass through the paper, so this would tell you nothing about the thickness of the paper. That brings you to, why is beta radiation used? Because some beta particles will pass through the paper, so the thickness of the paper can be determined by how many pass through to the detector.

Uses of Radiation (AQA GCSE Physics)

Revision Note