Three Types of Emissions & Half Life

Half-Life

The half-life is the average time taken for the number of radioactive nuclei to halve. Activity of a radioactive substance is measured in Becquerels (Bq).

Half-lives are predictable

• The radioactive decay of an individual atom is random and unpredictable.

• However, large groups of nuclei do normally behave in predictable ways.

Half lives are constant

• The half-life is the average time taken for the number of radioactive nuclei to halve.

• The half-life for any one isotope of an element is constant.

• The half-life of unstable isotopes can be seconds or millions of years.

The 3 Kinds of Ionising Emissions

Alpha, beta and gamma radiation all have different properties.

Alpha radiation

• Each alpha particle contains two protons and two neutrons.

• Because of this, alpha particles have a relative mass of 4.

• Because the particles are big and heavy, alpha radiation is strongly ionising.

• It does a lot of damage, but is stopped by a small amount of matter (like paper).

Beta radiation

• Beta radiation is made up of high-energy electrons.

• Beta radiation is more ionising than gamma radiation, but less ionising than alpha radiation.

• It can pass through paper, but is stopped by aluminium foil.

Gamma radiation

• Gamma radiation is weakly ionising.

• It does less damage than beta or alpha radiation, but it is stopped only by centimetres of lead or concrete.