Ionisation
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
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.
When
x-rays pass near a charged electroscope, the leaves converge,
indicating the creation of ions.
Demonstration
of ionisation
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.
Precautions
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.
Precautions
include;
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.