When an atom undergoes alpha or beta decay it can leave the nucleus in a high energy state. The atom goes to a lower energy state by emitting light. This light is very high energy (high frequency – short wavelength) and is called gamma (γ) radiation. The nucleus stays the same i.e. its atomic mass and atomic number do not change because all that has happened is that it has gone from a high energy state to a lower energy state.

Gamma radiation is always associated with another decay process such as alpha or beta decay.

Gamma rays usually have more energy and are more penetrating than X-rays. The thicker the shielding the fewer gamma rays can penetrate it but some always do.

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