Sunday, October 3, 2010

The Cathode Ray

Cutaway rendering of a color CRT:
1. Three Electron guns (for red, green, and blue phosphor dots)
2. Electron beams
3. Focusing coils
4. Deflection coils
5. Anode connection
6. Mask for separating beams for red, green, and blue part of displayed image
7. Phosphor layer with red, green, and blue zones
8. Close-up of the phosphor-coated inner side of the screen
The cathode ray tube is a vacuum tube containing a source of electrons, like an electron gun, it also has a fluorescent screen, with internal or external means to accelerate and deflect the electron beam. The cathode ray tube uses an evacuated glass envelope which is large, deep, heavy, and relatively fragile. The cathode ray is a stream of electrons in a vacuumed tube. An evacuated glass tube, equipped with at least two metal electrodes has a voltage applied to it. The voltage is a cathode or negative electrode and an anode or positive electrode. The cathode ray was first observed in 1869 by Johann Hittorf, a German physicist, but was named in 1876 by Eugene Goldstein kathodenstrahlen, or cathode rays. Electrons were first discovered using the cathode ray by J.J. Thomson in 1987. Thomas showed that the rays also had negatively charge particles, which were the electrons. Thomson found that the rays could be deflected by an energetic field. He was able to measure the particle's mass by comparing the deflection of a beam of cathode rays by electrical and magnetic fields. He discovered that they were 2000 times lighter than a hydrogen atom. He concluded that the rays had negatively charged particles.
One of the important things about the discovery of the electron was the electron microscope. It was invented in 1928 by Ernst Ruska. The electron microscope uses a stream of electrons to magnify something. Electrons have small wavelengths so they can be used to magnify objects that are too small to be resolved by light. Ruska used a strong magnetic field in order to focus the electrons into an image in a stream.

For information on how the cathode ray tube is go to: