Irradiation
Shining visible Energy carried by particles from a radioactive substance, or spreading out from a source. from a torch beam onto a hand lights the hand up because the hand has been exposed to light.
Exposing objects to beams of radiation is called Process of exposing an object to a source of radiation. Eg fruit exposed to gamma rays in order to destroy bacteria is said to have been irradiated.. The term applies to all types of radiation including radiation from the Nuclei is the plural of nucleus. The nucleus is the central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. of All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons..
Irradiation from The process in which unstable atomic nuclei break apart or change, releasing radiation as they do so. can damage living cells. This can be put to good use as well as being a hazard.
Irradiation for sterilisation
Irradiation can be used to preserve fruit sold in supermarkets by exposing the fruit to a When unstable atoms give off particles that can be harmful to humans. source - typically cobalt-60. The The shortest wavelength and highest energy part of the EM spectrum. Produced by radioactive materials. emitted by the cobalt will destroy any bacteria on the fruit but will not change the fruit in any significant way. The process of irradiation does not cause the irradiated object to become radioactive.
Medical irradiation
Doctors also use radioactive sources for a number of reasons, eg:
- The process of ensuring that a sample contains no living things. of surgical instruments
- beams of gamma rays, called a gamma knife, can be used to kill cancerous tumours deep inside the body
These beams are aimed at the tumour from many different directions to maximise the dose on the tumour but to minimise the dose on the surrounding soft tissue. This technique can damage healthy tissue, so careful calculations are done to establish the best dose - enough to kill the tumour, but not so much so that the healthy tissue is damaged.
In medical applications that involve using radioactive sources, efforts are made to ensure that irradiation does not cause any long-term effects. This is done by considering:
- the nature of decay (A type of ionising radiation consisting of 2 protons and 2 neutrons., A type of ionising radiation consisting of a single electron. or A type of ionising radiation that is also part of the EM spectrum. It has no mass.)
- the The time it takes for the number of nuclei of a radioactive isotope in a sample to halve. Also defined as the time it takes for the count rate from a sample containing a radioactive isotope to fall to half its starting level. (long enough for the isotope to produce useful measurements, but short enough for the radioactive sources to decay to safe levels soon after use)
- Poison level.
If the half-life chosen is too long, the damaging effects of the radiation would last for too long and the dose received would continue to rise.
Advantages and disadvantages of irradiation
Advantages
- sterilisation can be done without high temperatures
- it can be used to kill bacteria on things that would melt
Disadvantages
- it may not kill all bacteria on an object
- it can be very harmful - standing in the environment where objects are being treated by irradiation could expose peopleâs cells to damage and A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes.