- The three different types of radiation all have the ability to ionise gases:
- Alpha radiation is strongly ionising.
- Beta radiation is less ionising.
- Gamma radiation is only weakly ionising.
- Ionising ability and other properties can be used to detect radiation.
- There are a variety of instruments that can be used for radiation detection:
| Instrument |
Description
|
| Photographic film |
Darkens when exposed to radiation |
| Cloud chamber |
- Contains a supersaturated vapour of water or alcohol
- Radiation ionises some of the air, and the vapour condenses around the ions, tracing a path
|
| Geiger-Müller Counter |
- Consists of a conductive tube filled with argon gas, with a high voltage being connected to the outer casing and an electrode
- Radiation ionises argon atoms and the high voltage causes the resulting electrons to accelerate towards the electrode, ionising more argon atoms in their path
- The resulting cascade of electrons constitutes and electrical pulse, which is detected by a counter
|
| Scintillation counter |
- When certain substances are irradiated with alpha, beta or gamma rays (different substances for each type of ray), they emit a flash of light
- This flash can be collected and amplified in a photomultiplier
- The electric signal thus generated can operate an electric counter
|
Examples of radiation detection instruments
