Three types of Nuclear Radiation


This rock is radioactive. It must contain at least one unstable isotope and as this isotope decays it emits nuclear radiation. The ratemeter clicks as it detects the radiation and gives us a reading in counts per second.

The blue badge above contains a piece of photographic film when it is exposed to radiation the film, which starts white, is blackened. The darker it gets the more radiation has fallen on it.

There are 3 types of nuclear radiation that we need to know about.
They are named after the first 3 letters of the Greek alphabet; alpha, beta and gamma.

The three types of radiation have different properties. You should learn the table below.

  How far they can travel in air What is needed to stop them Are they deflected by magnetic fields Are they deflected by electric fields
alpha particles     α a few cm paper yes yes
beta particles       β 20 - 30 cm thin metal yes yes
gamma rays         γ several m thick lead no no


Alpha particles
These are very small, heavy, positively charged particles. They are made up of a little cluster of 2 protons and 2 neutrons stuck together. They do not travel as fast as the other 2 types of radiation. When moving through the air they bash into anything near them and do a lot of damage but lose their energy very quickly. Alpha particles are like cannon balls.

Beta particles
These are very small, light, very fast moving negatively charged particles. They are actually electrons which have come from the nucleus. (even though there aren't any in there!) Because they travel very fast they travel further than alpha particles. The damage they do is much more spread out. Beta particles are like bullets from a rifle.

Gamma rays
These are similar to X Rays. They are not particles but electromagnetic waves so they have no mass or charge and travel at the speed of light. They go through most things easily.

Alpha particles are like cannonballs. Heavy, slow but do a lot of damage. Beta particles are like bullets from a rifle. Small and fast and penetrating. Gamma rays are like the rays from Spock's phaser weapon. High energy waves.