| English | Beta particle |
|---|---|
| Bahasa Melayu | Zarah beta |
| 中文 | β粒子 |
Definition
A high-speed electron emitted from the nucleus when a neutron changes into a proton; it has a negative charge and moderate penetrating power.
In exam terms
A beta particle is a high-speed electron emitted from the nucleus when a neutron changes into a proton. It carries a charge of −1, is very light, and has moderate penetrating power, it passes through paper but is stopped by a few millimetres of aluminium.
A correct sentence: "A beta particle is emitted when a neutron in the nucleus becomes a proton, so the proton number increases by 1 while the nucleon number stays the same." It is less ionising than alpha but more ionising than gamma.
Do not confuse it with…
Do not confuse a beta particle with an ordinary orbiting electron. A beta particle comes from inside the nucleus (from a neutron turning into a proton), not from the electron shells, and it moves at very high speed.
Also distinguish it from an alpha particle: beta is lighter, less ionising and more penetrating, and is deflected in the opposite direction in a magnetic field.
In Paper 2 you may be asked to state what a beta particle is, explain how it is produced, or complete a decay equation where Z increases by 1 and A is unchanged.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)