![]() ![]() When a high voltage is applied between the electrodes, cathode rays ( electrons) are projected in straight lines from the cathode. ĭeveloped from the earlier Geissler tube, the Crookes tube consists of a partially evacuated glass bulb of various shapes, with two metal electrodes, the cathode and the anode, one at either end. ![]() The anode is the electrode at the bottom.Ī Crookes tube (also Crookes–Hittorf tube) is an early experimental electrical discharge tube, with partial vacuum, invented by English physicist William Crookes and others around 1869-1875, in which cathode rays, streams of electrons, were discovered. Electrons (cathode rays) travel in straight lines from the cathode (left), as shown by the shadow cast by the metal Maltese cross on the fluorescence of the righthand glass wall of the tube. The device is called an oscilloscope which is frequently used in medical treatment.Early type of cathode ray tube A Crookes tube: light and dark. Used to measure changes in electrical voltage with time. They helped the transition from the industrial age to the digital.ģ. Vacuum tubes were initially used in the place of silicon transistors in electronics. In old displays, vacuum tubes were used by directing the beam of electrons using deflection plates, then the beam causes fluorescence on the screen which we see as white.Ģ. So, the cathode ray experiment is also commonly known as J.J. The above modified experiments were performed by J.J. This also helped scientists in finding the charge of electrons. Hence, energy of electron at point A = energy of electron at point B Applying a Magnetic FieldĬathode rays also get deflected from their path if a magnetic field is applied. At point B the electron stops due to the activation of stopping potential, so we apply the law of conservation of energy between the two points. ![]() When electrons move from one point to another, say from A to B. When we apply electric field in parallel but in the opposite direction to the cathode rays and if it is sufficiently high for the cathode rays to stop, then the magnitude of the applied voltage is called stopping potential. The magnitude of deviation is proportional to the magnitude of the electric field. When cathode rays hit from the cathode travel towards the anode and hit the anode, a fluorescence or glow is produced.Ĭathode ray deviates from its path due to the application of an electric field. When a high voltage is applied between the two electrodes of an evacuated discharge tube and the back of anode of the discharge tube is coated with a material, like zinc sulfide. They were later named electronsafter particles postulated by George Johnstone Stoney. Thomson measured the weight of cathode rays and showed that they were actually a beam of particles. German scientists Eilhard Wiedemann, Heinrich Hertz and Goldstein said they were some new form of electromagnetic radiation. Scientists Crooks and Arthur Schuster said they were electrically charged atoms. Scientists came up with two theories regarding cathode rays when they were originally discovered. Eugene Goldstein was the one who actually gave cathode rays their name. Cathode rays were first identified by a German physicist named Johann Hittorf when he realized that something was travelling through the tube. ![]()
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