1. DETECTION OF NUCLEAR RADIATION
11.03

2. BACKGROUND RADIATION
There is a small amount of radiation around us because of radioactive materials in the environment. This is called background radiation. The sources are;
Ground and buildings
Granite rocks- radon gas
Medical
Cosmic rays from space,
nuclear test fallout, power stations, waste etc.

3. GEIGER MULLER (GM) TUBE
Used to detect alpha, beta and gamma radiations

4. The window is thin enough to allow radioactive particles to enter
when radioactive particles enter the tube, the gas inside is ionized
This sets off a high voltage spark and sends a pulse of current in the circuit

6. A ratemeter: gives the reading in counts per second
A scaler: counts the total number of particles detected by the tube
An amplifier & loudspeaker: makes a click when each particle or burst of gamma radiation is detected

7. The average reading of the background radiation must be found first and then subtracted from the total reading to get the radiation from a source.

8. Cloud chamber
It consists of a chamber with cold alcohol vapour in the air inside it
When alpha particles enter the chamber, the vapour condenses and a trail of tiny droplets are seen where each particle passes through

9. CLOUD CHAMBER