## AQA GCSE Physics

### Revision Notes

• 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

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.

• 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

#### Exam 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.

If you are presented with an unfamiliar situation in your exam don’t panic! Just apply your understanding of alpha, beta and gamma

### Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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