thomson cathode ray experiment lorentz law

#Thomson cathode ray experiment lorentz law series

Thomson constructed a modified Crookes tube as depicted in the above figure. Thomson decided to investigate further through another experiment. This resulted in a dilemma whether cathode rays are negatively charged particles or not. It was observed by Hertz well before Thomson. This statement became deficient when cathode rays failed to deflect in an electric field. The first experiment did demonstrate the behaviour of cathode rays as negatively charged particles under a magnetic field. The rays were independent of the material of electrodes and the gas in the jar.Cathode rays were deflected by a magnetic field in the same manner as if they were made up of negatively charged particles.He arrived at the two main points after this experiment. Moreover, he repeated the experiment with different materials and gases and found the deflection of the rays was the same irrespective of materials and gases used. “Thus this experiment shows that however we twist and deflect the cathode rays by magnetic forces, the negative electrification follows the same path as the rays and that this negative electrification is indissolubly connected with the cathode rays,” Thomson quoted. If these rays were further bent, they overshot the slits and the electrometer failed to show any readings. And the presence of negatively charge was detected in the electrometer. When the rays were bent by a magnetic field, they infiltrate the cylinders through the slits. He traced the path of the rays using the fluorescence on a squared screen in the jar. The rays would not enter the cylinders unless deflected by a magnetic field. When a high potential difference was applied between the cathode (A in the diagram) and anode (B in the diagram), cathode rays, which were produced in the left tube, emitted from the cathode and entered into the main bell jar.

The outer cylinder was grounded while inner was attached to an electrometer to detect any electric current as shown in the figure below. The cylinders were coaxial placed and insulated from each other. The experiment apparatus consisted of two metal cylinders. In the final experiment, he succeeded in measuring mass to charge ratio. In the first, the magnetic effect on cathode rays was studied while in the second, the rays were deflected by an electric field. His entire works can be divided into three different experiments. He concluded that the rays were comprised of particles. The immaterial nature and the aetherial hypothesis of cathode rays were proved wrong by J. According to some, the rays are due to some process in the aether. Many diverse opinions were held on these rays. Phosphorescent coating: It is the final part of the CRT, where the rays strike to create a glow.īack in those days, physicists were unclear whether cathode rays were immaterial like light or were material.Cathode rays bend as they interact with these fields. This is achieved by an external electric and magnetic field. Deflection system: It controls the direction of the electron beam.It will narrow the beam and increase its kinetic energy.

#Thomson cathode ray experiment lorentz law series

Focusing and accelerating system: It is made up of a series of anodes.

However, cold-cathode emission mechanism was used in Thomson's experiments. In modern CRTs, the electron beam is generated by thermionic emission-using a heating filament-as shown in the above diagram. It emits the sharp electron beam, cathode rays.

Electron emitter (or electron gun): The electron gun comprises of primarily heater and cathode.

The air in the tube is pumped out to create a vacuum. The cathode-ray tube (CRT) is a hollow glass tube. These rays travel in straight lines and can be deflected by electric and magnetic field. What are cathode rays? Cathode rays are streams of electrons emitted from the cathode (the electrode connected to the negative terminal of a battery). His experimental results were further investigated by Rutherford and Bohr, which further provided important insights into the atomic world.īefore directly jumping Thomson's findings, let us understand some basic knowledge on cathode rays and the cathode-ray tube.

However, Thomson's contributions remain more significant than the rest. Thomson was not the only one working on cathode rays, but several other players like Julius Plücker, Johann Wilhelm Hittorf, William Crookes, Philipp Lenard had contributed or were busy studying it. The apparatus of his experiment is called the cathode-ray tube (CRT). These particles later were named electrons. In 1897, he showed that cathode rays were composed of very small negatively charged particles. He was well-known for the discovery of the electron. Sir Joseph John Thomson was a British physicist and Nobel Laureate.