Physics Mid-topic check in GCSE Radiation

Isotope

Atoms of the same element with the same number of protons but a different number of neutrons;

Mass Number

Total number of protons and neutrons found in the nucleus of an atom;

Atomic Number

Number of protons found in the nucleus of an atom;

Background Radiation

Radiation that is present all around us from natural and man-made sources.

How to take the background radiation count

The background count must be taken and corrected for before measuring the activity of a radioactive sample.

1. Remove the radioactive source

2. Measure the background count over a 20 minute period

3. Find the activity= no of counts/no of seconds

4. Subtract the background count from further measurements of the radioactive source;

Alpha particle

Made of two protons and 2 neutrons, +2 charge, highly ionising, absorbed by a few cm of air or paper

In alpha decay: the atomic number decreases by 2 and the mass number decreases by 4;

Beta particle

A high energy electron, emitted from a nucleus when a neutron turns into a proton and an electron, -1 charge, moderately ionising, absorbed by 3mm aluminium

In beta decay: the atomic number increases by 1 and the mass number stays the same;

Gamma Ray

Part of the EM spectrum, no charge or mass, weakly ionising but highly penetrating, absorbed by lead or concrete.

Half Life

The average time it takes for the activity of a radioactive isotope to halve.

A sample with a longer half-life will decay more slowly and so is more stable;

Contamination

When a source of radiation is inside something/someone. A person can become contaminated by breathing in/swallowing or getting a source of radiation stuck in a wound or under a nail.;

Irradiation

When someone or something is exposed to radiation by being place near a source;

Ionising

Ionising radiation removes electrons from atoms. This is dangerous as it can cause mutations and cancers;

Random

You cannot predict which nucleus will decay next;

Spontaneous

External factors cannot force a nucleus to decay;