When the pressure of the gas in a discharge tube is lowered, at a certain stage the Crookes dark space fills the whole length of the tube. The fact that the walls of the tube glows (fluorescence) shows that something is coming out from the cathode, travelling through the length of the tube and falling on the walls. As we have discussed above, this something is a stream of fast-moving electrons. This fact was recognised after a series of experiments carried out by Crookes, Thomson and others.
Cathode rays are streams of electrons observed in vacuum tubes. Here’s a more human-friendly breakdown of their properties:
- Negatively Charged: Cathode rays are made up of electrons, which means they carry a negative charge.
- Straight Line Motion: They travel in straight lines, just like light beams. This is why shadows are cast when objects block cathode rays.
- Deflection by Electric and Magnetic Fields: Since they are charged particles, cathode rays can be bent or deflected by electric and magnetic fields. They bend in the direction you’d expect negatively charged particles to move.
- Energy-Dependent Penetration: Cathode rays can pass through thin materials, but how far they go depends on their energy. The higher the energy, the more they can penetrate.
- Fluorescence: When cathode rays strike certain materials, they can make them glow or fluoresce. This property is key in old-style TV screens and monitors.
- Heating Effect: They can heat up the object they hit. This is why cathode rays can make a metal target glow red-hot.
- Chemical Effects: Cathode rays can also cause chemical changes when they interact with certain materials, similar to how ultraviolet light can cause sunburn.
These are the main properties of cathode rays, presented in a way that’s easier to grasp.
