![]() ![]() He named the negatively charged particles. Cathode ray tube (CRT) - a vacuum-sealed tube in which electrons flow from the cathode. Thomson first developed this experiment in order to further understand the nature of cathode rays1. ![]() ![]() If we alter the potential difference between the Y-plates, the beam is deflected upwards or downwards on the screen. Thomson - an English physicist who used cathode rays to discover the existence of electrons in 1897. Usually, the potential difference applied to the X-plates makes the spot move across the screen at a uniform speed. This deflection is produced by two pairs of parallel plates arranged at right angles. If necessary the stream of emerging electrons can be deflected in its passage between the gun and the screen. How did it work and why did Thomson do the experiment in the first place Watch the video and. On leaving the gun, the electron stream passes across the tube and eventually hits the screen at the far side. In 1897, JJ Thomson discovered the electron in his famous cathode ray tube experiment. Such arrangement of electrodes where a stream of electrons is produced is often known as the electron gun. As a result, the electrons accelerate across the gap between the electrodes and a narrow stream of the electrons emerges from the hole in the anode. A potential difference of some hundreds of volts is applied between cathode and anode. At a short distance from the cathode is an anode having a central hole in it. In the oscilloscope, the electrons are emitted by a hot cathode which is situated in a highly evacuated tube. The oscilloscope has many points in common with the discharge tube. The glow produced by the fast moving electrons on a fluorescent screen led to its use in radar and television. Cathode Ray Tube - The Cathode Ray Experiment by J.J.Thomson helped to discover electrons. So much so, that George Stoney (1891) proposed the name electron for the particle. Scientist had believed in the existence of a negative particle for some time. Cathode rays are normally invisible beams of particles that can be contained within vacuum tubes for observation. Image: Draw a fine-beam tube with annotations/labels. Thomson was experimenting with cathode rays. Thomson demonstrated the existence of the electron. What four things did JJ Thomson demonstrate about cathode rays 1. The discovery of cathode rays led to a vast field of practical application in Electronics. The cathode ray tube experiment performed by J.J. Modern cathode ray tubes have hot cathodes which require much less voltage, nearly 3000 volts. It needed a high voltage of the order of 30,000 volts. The cathode, in the discharge tubes used by Sir Thomson, was cold cathode. Experiments showed that mass of the electron is approximately 1/1860 of mass of hydrogen atom. ![]() Thomson found that the electrons had mass far less than of even the hydrogen atom. We know that hydrogen atom is the lightest atom. Thomson found that cathode rays always had the same e/m ratio, no matter what metals were used for the cathodes and no matter what gas was used in the tubes. As these emanate from the cathode, the rays are called the Cathode Rays. These electrons emanate normally from the cathode. When this fluorescence was investigated, it was found that the fluorescence consisted of beams of negatively charged electrons. \): Millikan’s experiment measured the charge of individual oil drops.When the pressure in the discharge tube is less than 10 -4 mm of Hg, the discharge tube starts showing fluorescence. ![]()
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