*1.3.2 Beta particles*

Beta particles are high-speed electron or positron emitted from the radioactive decay of an atomic nucleus such as potassium-40 during beta decay. These particles

**Figure 1.** *Various type of DNA damage induce by radiation.*

are emitted by unstable nuclei rich in neutrons, they are high energy electrons. These particles are negatively charged and have intermediate penetration power [5].

## *1.3.3 Gamma rays*

Gamma radiation, unlike alpha or beta, does not consist of any particles; instead, they consist of a photon of energy being emitted from an unstable nucleus. These are produced by a change in the energy levels of the atomic nuclei. The wave length of this radiation varies from 0.0003 nm to 0.1 nm. Gamma rays do not have any mass or charge. It can travel at much higher speed in air than alpha or beta rays and loses only half of its energy for every 500 feet. Gamma rays can be stopped by dense and thick layer of material such as lead or depleted uranium. These materials are used as an effective shielding in radiation related work [5].

## *1.3.4 X-rays*

X-rays are generated from electron cloud when electron moves from higher energy level to lower energy level causing excess energy to be released. It is very similar to gamma radiation [5].
