18. 4 Uses of Radio Isotopes
Although, all the isotopes of an element chemically behave identically, but every isotope emits specific radiations due to which it is easy to identify an isotope. It is this characteristic due to which the isotopes are being used in different fields of our life.
Uses in agriculture
If the seeds are unhealthy, they affect the agricultural yield. So such seeds are exposed to radioactive radiations. Varieties of seeds are prepared which are more resistant to the ailments of crops. Also by using such seeds higher yield is achieved.
Uses in medicine
Radio isotopes are used to diagnose the various diseases and also for curing some fatal diseases. The radiations from radio active materials are used to diagnose the internal disease of the body without surgery. For example, lodine-131 is used for the study of thyroid glands while phosphorus-32 is used to diagnose the brain tumor.
The parts suffering from cancer absorb more quantity of isotopes, and thus indicate the correct position f the diseased part which helps in the treatment. Some types of cancers are also cured by radio isotopes. For example, radioactive cobalt-60 is used for curing cancerous tumors and cells.
18. 5 Einstein’s mass energy equation
Although in classical physics, the various forms of energy were related under the law of conservation of energy but no relationship was established between the energy and mass. In 1905, when Einstein gave his theory of relativity, it also contained the idea that the energy and matter are interchangeable. For this change an equation was also given which is known as Einstein’s mass-energy equation. It is
Which means that if mass M of matter is converted into energy, then this will be equal to E, where in this equation c is the speed of light 
Example 18.2: find the energy produced from 20 kg of carbon if it is completely changed into energy.
Solution:
For your information
- Measuring unit of nuclear radiations is rem.
- Patient should be exposed to X rays within the limit of 0. 1 to 1.0 rem.
- 5.0 rem per year is considered as safe limit.
Do you know?
Sources of nuclear rays are natural as well as man made. Natural sources are radon gas radioactive elements while Xrays. T.V. nuclear power plants are man made sources.