Sir Williama Crooks (1832-1919), built up
Varley'a conception. Crooks conducted many important
experiments using self-made vacuum tubes. He noticed that the thin foil on which the beam
of cathode rays was focused got hot. That proved that the rays, whatever they were,
transferred energy. The second thing he discovered was that the beam of rays exerted some
force - transferred momentum. He demonstrated that using the paddle wheel which he put
inside the vacuum tube. The paddles were in such direction as to be influenced by the
rays' incidence. The wheel could roll in the tube when there was some force influencing
the paddles (the friction was minimized). The tube laid horizontal. The wheel began to
move when the cathode rays illuminated the paddles. For Crooks that movement proved
that the cathode rays influenced the paddles with some force. But, in 1903, in his book
"Conduction of Electricity Through Gases" Thomson
proved that the force with which the cathode rays influenced the paddles was not strong
enough to induce such a fast movement. So Thomson proved
that the movement was really induced by the radiometric effect - the paddles were not
uniformly heated - The heated and unheated sides of the paddles received different momentum
from the particles of the gas in the tube. The only thing proven by the Crooks's
experiment was that cathode rays heated the paddles. But in the eighties the experiment was
treated the proof for cathode rays transferring momentum. Crooks was studying the structure of the cathode rays and the reason for them being induced. In the model, he created, the particles of the tail gas in the tube collided with the cathode and that way got negatively charged. After that the particles were repulsed by the cathode, getting high speed. That was because the cathode and the particles were the same charged. The particles, repulsed perpendicular with the respect to the cathode, passed through the cathode dark space and then induced illumination by collisions with the other particles. Such model explained the most of the cathode rays' features and phenomena. |
Tait yet in 1880 noticed a big mistake in the Crooks's theory although the theory developed in the fall of 70ths of the 19th century. Tait noticed that if cathode rays were really fast moving particles then the light waves emitted by them should be characterized by Doppler shift. They weren't. |
Wiedemann and the two other German scientists - Eugen Goldstein and Heinrich Hertz - created a different model explaining features of cathode rays. They came to the opinion that cathode rays couldn't consist of particles but were of wave structure. Their conclusion was caused by the fact that all features of cathode rays were the same as of electromagnetic waves. The difference laid only in the two things: the first is that waves don't undergo aberration in the magnetic field and as cathode rays do, and the second is that the waves are emitted in all directions with respect to the surface and the cathode rays are emitted only perpendicular with respect to the surface of the cathode. The authors of the theory stated that the differences could be explained by some unknown features of eteru and by the electrical nature of the rays creation. |
Artur Schuster, who was English was one of the most important sympathizer of the corpuscular theory for the cathode rays. In his opinion not the moving particles were the source of light but the immovable particles of the gas with which the particles of rays collide. That is why, as he said, the Doppler shift doesn't occur. Also the created by Schuster model of the particles was different; the atoms of the gas dissociate for the positive and negative parts. The positive particles are collected by the cathode and the negative parts are repulsed from it - they create the beam of the cathode rays. He conducted also the experiment where he estimated the maximum and minimum limits of the q/m. (where q is the charge, m. is the mass of the hypothetical particle. |
Since 1705 scientists have discovered many features of the cathode rays.
Such great scientists like . Goldstein,
Schuster, Hertz and Lenard were
studying them. They were for the two different, competitive theories for the cathode rays'
behavior - the wave and the corpuscular one. Only just in 1897 the more exact model of
cathode rays was formulated. You can read about that in the chapter "The Thomson's experiment".