- They are electromagnetic waves of wavelengths shorter than those of X-rays
- Electrically neutral, are not deflected by electric and magnetic fields.
- Among the three types of radiation, gamma rays have the strongest penetration power. Gamma rays are stopped by lead of a few centimetres thick
- Ionisation power of gamma rays is about 1/10 000 that of alpha particles
- Their emission does not accompany any change in nuclear structure; the nucleus merely descends to a lower energy state.
- Gamma decay represents the emission of energy from a nucleus which is returning to its ground state.
Excited nucleus → more stable nucleus + γ