![]() ![]() Then Thomson compared his result with the magnetic deflection of the rays.Īs a result, Thomson could suggest that cathode rays were more than 100 times lighter than the hydrogen atom and also, he concluded that their mass was the same in whichever type of atom they came from. At first, he estimated the mass of cathode rays through the heat that was generated when the rays hit a thermal junction. He published his suggestion on 30 April 1897 following his discovery that Lenard rays could travel much further through air than expected for an atom-sized particle. To achieve this discovery, Thomson used his explorations on the properties of cathode rays. Today, the subatomic particle is known as the electron. Thomson was the first known scientist to suggest that the fundamental unit was over 1000 times smaller than an atom. ![]() The fact that atoms were built up from a more fundamental unit was already suggested by scientists like William Prout or Norman Lockyer. Thomson’s Cavendish Laboratory in the first years of the 1900s, as quoted “The electron: may it never be of any use to anybody!” In 1918, Thomson became Master of the Trinity College in Cambridge. Thomson himself was awarded the famous prize in 1906 “ in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases.” Two years later, he was knighted. Seven of his research assistants and his son were able to win the Nobel Prizes in physics. Thomson was known to be an excellent teacher. When Thomson became Cavendish Professor of Physics, Ernest Rutherford was among his students and later on, he succeeded Thomson in the post. In 1876, he enrolled at Trinity College, Cambridge where he received his Bachelor’s and Master’s degree. Joseph John Thomson was born in 1856 in Manchester, England and was taught mainly in private schools at the beginning. Thomson, “Cathode rays” Philosophical Magazine, 44, 293 (1897). “As the cathode rays carry a charge of negative electricity, are deflected by an electrostatic force as if they were negatively electrified, and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter.” Thomson was awarded the 1906 Nobel Prize in Physics for the discovery of the electron and for his work on the conduction of electricity in gases. If we alter the potential difference between the Y-plates, the beam is deflected upwards or downwards on the screen.On April 30, 1897, English physicist Joseph John Thomson gave the first experimental proof of the electron, which had been already theoretically predicted by Johnstone Stoney. 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. On leaving the gun, the electron stream passes across the tube and eventually hits the screen at the far side. 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. The discovery of cathode rays led to a vast field of practical application in Electronics. 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. 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. When the pressure in the discharge tube is less than 10 -4 mm of Hg, the discharge tube starts showing fluorescence. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |