Radioactivity

Radioactivity is the emission of energetic particles or waves from atoms. Natural radiation occurs when unstable nuclei transform to some other nucleus by emitting radiation. Induced radiation often occurs when electrons which have been excited lose energy in the form of X-rays or microwaves, as done in  microwave ovens  and radar.

Types of Radioactive rays

Rutherford seperated the radio active emissions into three by passing them through a strong electric field between two parallel plates.The three radioactive rays are α-rays,β -rays,γ -rays.

Types of Radioactive rays

Types of Radioactive rays

α-rays

These rays get deflected towards the negative plate or they carry positive charge.The particles in these rays alpha particles contain helium nuclei.They are shot out from the radio active material at high velocities ranging from 1.4 × 10     to 1.7 × 109           cms per second

 

They produces intense ionization of the gas through which they pass.Their ionizing power is 100times greater than that of  β -rays and 10000 times grater than that of  γ -rays.Among the three radioactive radiation alpha rays have the shortest penetrating power.

β -rays

Beta particles are energetic electrons that are emitted from the nucleus. They are born when a neutron decays to a proton. Since neutrons are neutral particles and protons are positive, conservation of charge requires a negatively charged electron to be emitted. Some isotopes decay by converting a proton to a neutron, thus emitting a positron (an anti-electron). These particles can penetrate matter more than can alpha particles, and it takes a small aluminum plate to stop most beta particles.Its velocity ranging from one percent to 99 percent of the velocityof light.It can penetrats through large thickness of matter almost 100 times than the alpha particles.

γ -rays

 Gamma rays are photons that are emitted from the nucleus. Often an atom in an excited state will de-excite by emitting a gamma ray. Gamma rays are similar to light waves and x rays, except they are usually much higher frequency and consequently, more energetic. This radiation has no charge, and can penetrate most matter easily, requiring a lead brick for shielding.Its velocity is same as light .Their ionizing power is comparitivly small but their penetrating power is highest among radioactive rays.