| English | Gamma ray |
|---|---|
| Bahasa Melayu | Sinar gama |
| 中文 | γ射线 |
Definition
A high-frequency electromagnetic wave emitted by an unstable nucleus; it has no charge and very high penetrating power.
In exam terms
A gamma ray is a high-frequency electromagnetic wave emitted by an unstable nucleus, usually just after alpha or beta emission when the nucleus still has excess energy. It has no charge and no mass, and very high penetrating power, it needs thick lead or concrete to reduce it.
Being an EM wave, it travels at the speed of light, about 3.0 × 10⁸ m s⁻¹ in a vacuum.
A correct sentence: "Gamma rays are the most penetrating but least ionising of the three radiations." Emitting a gamma ray does not change the nucleon number or the proton number.
Do not confuse it with…
Do not confuse a gamma ray with alpha and beta radiation. Gamma is a wave with no charge, so it is not deflected by electric or magnetic fields, whereas alpha (+2) and beta (−1) are particles that are deflected.
Also distinguish gamma rays from X-rays: both are EM waves, but gamma comes from the nucleus while X-rays are produced outside the nucleus.
In Paper 2 you may be asked to state the nature of a gamma ray, explain why it is not deflected in a magnetic field, or compare its penetrating and ionising power with alpha and beta.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)