Cathode Ray Tube History

1855 German inventor Heinrich Geissler develops mercury pump - produces first good vacuum tubes, these tubes, as modified by Sir William Crookes, become the first to produce cathode rays, leading eventually to the discovery of the electron (and a bit farther down the road to television).

1858 Julius Plücker shows that cathode rays bend under the influence of a magnet suggesting that they are connected in some way; this leads in 1897 to discovery that cathode rays are composed of electrons.

1865 H. Sprengel improves the Geissler vacuum pump. Plücker uses Geissler tubes to show that at lower pressure, the Faraday dark space grows larger. He also finds that there is an extended glow on the walls of the tube and that this glow is affected by an external magnetic field.

1869 J.W. Hittorf finds that a solid body put in front of the cathode cuts off the glow from the walls of the tube. Establishes that "rays" from the cathode travel in straight lines.

1871 C.F. Varley is first to publish suggestion that cathode rays are composed of particles. Crookes proposes that they are molecules that have picked up a negative charge from the cathode and are repelled by it.

1874 George Johnstone Stoney estimates the charge of the then unknown electron to be about 10-20 coulomb, close to the modern value of 1.6021892 x 10-19 coulomb. (He used the Faraday constant (total electric charge per mole of univalent atoms) divided by Avogadro's Number. James Clerk Maxwell had recognized this method soon after Faraday had published, but he did not accept the idea that electricity is composed of particles.) Stoney also proposes the name "electrine" for the unit of charge on a hydrogen ion. In 1891, he changes the name to "electron."

1876 Eugen Goldstein shows that the radiation in a vacuum tube produced when an electric current is forced through the tube starts at the cathode; Goldstein introduces the term cathode ray to describe the light emitted.

1881 Herman Ludwig von Helmholtz shows that the electrical charges in atoms are divided into definite integral portions, suggesting the idea that there is a smallest unit of electricity.

1883 Heinrich Hertz shows that cathode rays are not deflected by electrically charged metal plates, which would seem to indicate (incorrectly) that cathode rays cannot be charged particles.

1886 Eugen Goldstein observes that a cathode-ray tube produces, in addition to the cathode ray, radiation that travels in the opposite direction - away from the anode; these rays are called canal rays because of holes (canals) bored in the cathode; later these will be found to be ions that have had electrons stripped in producing the cathode ray.

1890 Arthur Schuster calculates the ratio of charge to mass of the particles making up cathode rays (today known as electrons) by measuring the magnetic deflection of cathode rays. Joseph John (J.J.) Thomson first becomes interested in the discharge of electricity through a gas a low pressure, that is to say, cathode rays.

1892 Heinrich Hertz who has concluded (incorrectly) that cathode rays must be some form of wave, shows that the rays can penetrate thin foils of metal, which he takes to support the wave hypothesis. Philipp von Lenard develops a cathode-ray tube with a thin aluminum window that permits the rays to escape, allowing the rays to be studied in the open air.

1894 J.J. Thomson announces that he has found that the velocity of cathode rays is much lower than that of light. He obtained the value of 1.9 x 107 cm/sec, as compared to the value 3.0 x 1010 cm/sec for light. This was in response to the prediction by Lenard that cathode rays would move with the velocity of light. However, by 1897, he distrusts this measurement.

Special Note: At this time there was great rivalry between German and British researchers. As concerning the nature of the cathode ray, the Germans tended to the explanation that cathode rays were a wave (like light), whereas the British tended to believe that the cathode ray was a particle. As events unfold over the next few decades, both will be proven correct.

In fact, J.J. Thomson will be awarded the Nobel Prize in Physics in 1906 for proving the electron is a particle and his son, George Paget Thomson, will be awarded the Nobel Prize in Physics in 1937 for showing that the electron is a wave.

1895 Jean-Baptiste Perrin shows that cathode rays deposit a negative electric charge where they impact, refuting Hertz's concept of cathode rays as waves and showing they are particles.

1896 Pieter P. Zeeman discovers that spectral lines of gases placed in a magnetic field are split, a phenomenon call the Zeeman effect; Hendrik Antoon Lorentz explains this effect by assuming that light is produced by the motion of charged particles in the atom. Lorentz uses Zeeman's observations of the behavior of light in magnetic field to calculate the charge to mass ratio of the electron in an atom, a year before electrons are discovered and 15 years before it is known that electron are constituents of atoms.