Electrons (cathode rays) travel in straight lines from the cathode (left), as shown by the shadow cast by the metal Maltese cross on the fluorescence of the righthand glass wall of the tube. The technology of controlling electron beams resulted in the invention of the amplifying vacuum tube in 1907, which created the field of electronics and dominated it for 50 years, and the cathode ray tube which was used in radar and television displays.A Crookes tube: light and dark. Thomson showed that cathode rays consisted of a previously unknown particle, which was named the electron. Observing that sharp-edged shadows were cast on the glowing tube wall by obstructions in the tube in front of the cathode, Johann Hittorf realized that the glow was caused by some type of ray travelling in straight lines through the tube from the cathode. When current was applied, it was found that the glass envelope of these tubes would glow at the end opposite to the cathode. By the 1870s better vacuum pumps enabled scientists to evacuate Geissler tubes to a higher vacuum these were called Crookes tubes after William Crookes. One of the most significant consequences of Geissler tube technology was the discovery of the electron and the invention of electronic vacuum tubes. Geissler tubes were the first gas discharge tubes, and have had a large impact on the development of many instruments and devices which depend on electric discharge through gases. ![]() Geissler tubes are sometimes still used in physics education to demonstrate the principles of gas discharge tubes. Another example of their use was to find nodes of standing waves on transmission lines, such as Lecher lines used to measure the frequency of early radio transmitters.Īnother use around 1900 was as the light source in Pulfrich refractometers. They were used to tune the tank circuits of radio transmitters to resonance. When a Geissler tube was brought near a source of high voltage, alternating current, such as a Tesla coil or Ruhmkorff coil, it would light up even without contact with the circuit. Simple straight Geissler tubes were used in early-20th-century scientific research as high voltage indicators. ![]() When an operating tube was touched by the hand, the shape of the glowing discharge inside often changed due to the capacitance of the body. A novel effect could be obtained by spinning a glowing tube at high speed with a motor a disk of color was seen due to persistence of vision. Some tubes were very elaborate and complex in shape and would contain chambers within an outer casing. Geissler tubes were mass-produced from the 1880s as novelty and entertainment devices, with various spherical chambers and decorative serpentine paths formed into the glass tube. In the early 20th century, the technology was commercialized and evolved into neon lighting.Īpplication Straight Geissler tubes filled with various gases The first gas-discharge lamps, Geissler tubes were novelty items, made in many artistic shapes and colors to demonstrate the new science of electricity. The color of light emitted is characteristic of the material within the tube, and many different colors and lighting effects can be achieved. ![]() The current dissociates electrons from the gas molecules, creating ions, and when the electrons recombine with the ions, the gas emits light by fluorescence. When a high voltage is applied between the electrodes, an electric current flows through the tube. It consists of a sealed, partially evacuated glass cylinder of various shapes with a metal electrode at each end, containing rarefied gasses such as neon, argon, or air mercury vapor or other conductive fluids or ionizable minerals or metals, such as sodium. The tube was invented by the German physicist and glassblower Heinrich Geissler in 1857. (right) Geissler tubes at museumĪ Geissler tube is an early gas discharge tube used to demonstrate the principles of electrical glow discharge, similar to modern neon lighting. (left) Drawing of typical Geissler tubes from 1911 encyclopedia.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |