| English | Cathode ray |
|---|---|
| Bahasa Melayu | Sinar katod |
| 中文 | 阴极射线 |
Definition
A stream of fast-moving electrons emitted from a cathode and travelling towards the anode in a vacuum tube.
In exam terms
A cathode ray is a stream of fast-moving electrons emitted from a cathode and travelling towards the anode inside a vacuum tube. The electrons are produced by thermionic emission and accelerated by a high potential difference between the cathode and anode.
Because they are electrons, cathode rays carry negative charge and can be deflected by electric and magnetic fields.
Example of correct use: in a cathode-ray oscilloscope, the cathode ray strikes a fluorescent screen and produces a bright spot that traces out the input signal.
Do not confuse it with…
Do not confuse a cathode ray (a beam of electrons, which are particles) with a gamma ray or other electromagnetic wave. A cathode ray has mass and charge and is deflected by fields; an electromagnetic wave has neither and is not deflected.
In Paper 2 you may be asked to state the properties of cathode rays or to explain how they are deflected; remember they move from cathode (negative) to anode (positive) and are attracted towards a positive deflecting plate.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)