![]() For the experiment, he used the cathode ray tube and with a high applied potential difference between the two electrodes, with the negatively charged cathode producing the cathode rays. Then he performed the third experiment, to know the nature of the particles and reduce the mass of the particles as they had too small of a mass to be calculated directly. This proved that the cathode rays were negatively charged. ![]() When the charged metal plates were introduced he found that the cathode rays bent away from the negative plate and towards the positive plate. ![]() Instead of an electrometer at one end of the Cathode Ray Tube, he used a fluorescent coated tube that would glow where the cathode ray hit it. Now, he put a negatively charged metal plate on one side of the cathode rays to go past the anode, and a positively charged metal plate on the other side. Then he conducted a Second experiment, to prove the charge carried by the cathode rays was negative or positive. From this, he deduced that the electric charge and the cathode rays must be combined and are the same entity. From the first experiment, he discovered that the electrometers stopped measuring electric charge. The metal had two small diversions(slits), leading to an electrometer that could measure a small electric charge. He built his cathode ray tube with a metal cylinder on the other end. Thompson, conducted his first cathode ray tube experiment to prove that rays emitted from an electron gun are inseparable from the latent charge. Screen: - The inner layer of the screen is coated with phosphorus, and produces fluorescence when cathode rays hit the screen by a process of phosphorus excitation.Īquadag: - It is an aqueous solution of graphite used to collect the secondary emitted electrons which are required to keep the cathode ray in electrical equilibrium. The electron gun has a heater, cathode, pre-accelerating anode, focusing anode and accelerating anode.ĭeflecting Plates: - They produce a uniform electrostatic field only in one direction, and accelerate particles in only one direction. A wire is connected from anode to cathode to complete the electrical circuit.Įlectron Gun Assembly: - It is the source of the electron beams. When a potential difference is applied, the electrons jump to an excited state and travel at high speeds to jump back-and-forth inside the vacuum glass chamber and when some cathode rays certain molecules of the cathode screen, they emit light energy. Since electrons are repelled by the negative electrode, the cathode is the source of cathode rays inside a vacuum environment. The cathode is a negative electrode, Anode is the positive electrode. Normal glass isn't particularly luminescent so tubes designed to produce light (like a CRT) are coated with phosphors.Cathode rays are a beam of negatively charged electrons traveling from the negative end of an electrode to the positive end within a vacuum, across a potential difference between the electrodes. Basically, the electrons striking the glass excite components of the glass to an elevated electronic state which releases light upon returning to the ground state. The glow of the glass envelope is luminescence-either fluorescence or phosphorescence (or both). ![]() In cold cathodes, electrons are released by field emission, where a large applied electric field allows electrons to tunnel away from a metal electrode. The electron beam is produced by thermionic emission in hot cathodes-electrons are liberated from a hot filament when the thermal energy is enough for electrons to exceed the filament's work function. If there's enough gas, you get a plasma rather than a beam of electrons. The vacuum doesn't have much to do with the production of electrons, per se, but without high vacuum, the electrons collide with gas particles before they travel very far. The sharp shadows produced by Crookes tubes meant that something was travelling in a straight line from the cathode down the tube, so they were named cathode rays. The name exists because cathode ray devices predate the discovery of the electron. "Cathode rays" are simply beams of electrons.
0 Comments
Leave a Reply. |