stream of electrons observed in vacuum tubes / From Wikipedia, the free encyclopedia
A cathode ray is a stream of electrons that are seen in vacuum tubes. It is called a "cathode ray" because the electrons are being emitted from the negative charged element in the vacuum tube called the cathode. A cathode ray tube aims the ray at a point on its screen. They were first observed in 1869 by German physicist Johann Hittorf, and were named in 1876 by Eugen Goldstein Kathodenstrahlen, or cathode rays.
Electrons were discovered as the constituents of cathode rays in 1897 by British physicist J. J. Thomson. He showed the rays were composed of a previously unknown negatively charged particle, which was later called the electron. Cathode ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to create the image in a classic television set.
Some properties of cathode rays:
- They travel in a straight path.
- They have a negative electric charge
- They have particle property
- Magnets can deflect them
- Charge/mass ratio of the rays is constant
- They travel from the cathode to the anode
- Their properties are independent from the electrodes and gas present in the cathode ray tube.
- Cathode rays can ionize gas
- The travel more slowly than light
- They can heat objects that they hit
- They can penetrate through thin Aluminium plates
- They can make phosphors glow