1. Gamma rays are electromagnetic waves of very short wavelength. Speed of γ –rays equals c.
2. Gamma rays are often emitted in conjunction with β particles.
3. They produced flourescene and affect photographic plates.
4. They are reflected from the surface of a crystal. This property of γ rays is used to measure their wavelength.
5. They ionize gases very slightly.
6. γ rays have greater pentrating power than α or β rays.
According to the development in the field of nuclear models it is now known that there are energy levels in the nucleus just like atoms (of the order of μeV). When the nucleus is in an excited satte it can make a transition to a lower state by the emission of electromagnetic radiations.
Most radioactive nucleus after an alpha or beta emission leave the resultant nucleus in an excited state. This nucleus known as daughter nucleus reaches the ground state by a single or sometimes successive transition by emitting one or more gamma rays.