All matter is made up of atoms. These atoms consist of a nucleus containing positive charges, surrounded by electrons (which are negatively charged). Matter in its normal state contains atoms which have no net electrical charge (i.e. equal numbers of both positive and negative charge). Ionisation is the removal of electrons from atoms.
The removed electron is a negative ion and the remaining positively charged atom is a positive ion. Energy is needed to remove an electron against the attractive force holding it to the atom. Thus ionisation requires energy.
Ionising radiation differs from other forms of radiation, e.g. visible light, in that it has sufficiently high energy to cause ionisation when it interacts with matter.
x-rays pass near a charged electroscope, the leaves converge,
indicating the creation of ions.
An important characteristic of x-rays is their ionizing power, which depends upon their wavelength. The capacity of monochromatic x-rays to ionize is directly proportional to their energy. This property provides a method for measuring the energy of x-rays. When x-rays are passed through an ionization chamber, an electric current is produced that is proportional to the energy of the incident beam.
Danger posed by ionising radiation
The effect on
humans of ionising radiation depend on;
1. the type of radiation
2. the type of tissue irradiated
3, the duration of the exposure.
The consequences of over-exposure to ionising radiation, like x-rays, include; burns, cancers and genetic defects.
We are all exposed to a certain level of ionising radiation, referred to as background radiation.
Its important to minimise ones exposure to
any additional ionising radiation.
1. Make sure sources are properly shielded.
2. Use protective clothing (e.g. goggles and gloves).
3. Minimise the time of exposure.
4. Keep as far from the source as possible.