The existence of negatively charged particle in an atom was shown b...
0The existence of negatively charged particle in an atom was shown by \( \mathbf{J} \mathbf{J} \). Thomson as a result of the studies of the passage of electricity through gases at extremely low pressures known as discharge tube experiments. When a high voltage of the order of 10,000 volts or more was impressed across the electrodes, some sort of invisible rays moved from the negative electrode to the positive electrode these rays are called as cathode rays.
For cathode rays the value of \( e / m \) :
Cathode rays experiment Cathode rays travel in straight path in absence of electrical and magnetic field. Cathode rays consist of material part and charged particles? Cathode (a) is independent of the nature of the cathode and the gas filled in the discharge tube
(b) is constant field. Cathode rays consist of material part and charged particles? Cathode
(c) is \( -1.7588 \times 10^{8} \) coulombs \( / \mathrm{g} \) rays produce \( \mathbf{X} \)-rays and light is emitted when they strike on \( \mathrm{Z} \) S screen. Cathode rays penetrate through thin sheets of aluminium and other metals. They affect the photographic plate and passes heating effect when they strike on metal foil. The ratio of charge to mass i.e. charge/mass is same for all the cathode rays irrespective of the gas used in the tube.
The existence of positively charged particles in an atom was shown by \( \mathbf{E} \). Goldstein. He repeated the same discharge tube experiments by using a perforated cathode. It was observed that when a high potential difference was applied between the electrodes, not only cathode rays were produced but also a new type of rays were produced simultaneously from anode moving towards cathode and passed through the holes or canal of the cathode. These termed as canal rays or anode rays.
These rays travel in straight lines and consist of positively charged particles. These rays have kinetic energy and produces heating effect also. The \( \mathrm{e} / \mathrm{m} \) ratio of these rays is smaller than that of electrons. Unlike cathode rays, their \( e / m \) value is is dependent upon the nature of the gas taken in the tube. These rays produce flashes of light on \( \mathrm{ZnS} \) screen and can pass throughs thin metal foils. They can produce physical and chemical changes and are capable to produce ionisation in gases.
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