CONTROL OF MICROORGANISMS BY PHYSICAL METHOD..
- X-rays: They are electromagnetic waves with wavelength smaller than 10nm. X-rays are lethal to mos & higher organisms. However, they are impracticable for controlling mos because they are expensive to produce, difficult to handle efficiently & since radiations are given off in all directions from the point of origin .However, X-rays are important in producing microbial mutants. (http://en.wikipedia.org/wiki/Mutagenesis)
- Gamma rays: They have wavelength of 10^-3 to 10^-2 nm . It is high energy yielding radiation emitted from certain radioactive isotope of Cobalt .Gamma rays are similar to x-rays but of shorter wavelength & high energy. Gamma rays are used in commercial sterilization of materials with high thickness & volume like package of food & medical devices.