Katodisäteilyä

Katodisäteilyä, also known as cathode rays, refers to a stream of electrons emitted from the cathode of a vacuum tube. These rays are negatively charged particles and were crucial in early experiments that led to the discovery of the electron. When a high voltage is applied across electrodes in a vacuum or a low-pressure gas, the cathode emits electrons, which then travel towards the anode.

The properties of cathode rays were systematically studied by physicists in the late 19th century. It was observed that these rays could be deflected by electric and magnetic fields, indicating they were composed of charged particles. J.J. Thomson's experiments in 1897 were particularly significant, as they demonstrated that cathode rays were indeed fundamental particles, which he called "corpuscles," later named electrons. Thomson also measured the charge-to-mass ratio of these particles.

Cathode rays were instrumental in the development of early electronic devices such as the cathode ray tube (CRT), which was widely used in oscilloscopes, televisions, and computer monitors. In a CRT, a beam of electrons is directed onto a phosphorescent screen, causing it to glow and create an image. While CRTs have largely been replaced by newer technologies like LCD and OLED, the understanding of cathode rays laid the groundwork for much of modern electronics and particle physics.