3 ms·

Do you have a basis for not believing it aside from you having a different theory?

• pfdietz 3y ago
  You will note that incandescent bulbs gradually get dimmer as they age, due to deposition of tungsten on the glass. Also: http://donklipstein.com/bulb1.html http://donklipstein.com/bulb1.html "Due to the high temperature that a tungsten filament is operated at, some of the tungsten evaporates during use. Furthermore, since no light bulb is perfect, the filament does not evaporate evenly. Some spots will suffer greater evaporation and become thinner than the rest of the filament. These thin spots cause problems. Their electrical resistance is greater than that of average parts of the filament. Since the current is equal in all parts of the filament, more heat is generated where the filament is thinner. The thin parts also have less surface area to radiate heat away with. This "double whammy" causes the thin spots to have a higher temperature. Now that the thin spots are hotter, they evaporate more quickly. It becomes apparent that as soon as a part of the filament becomes significantly thinner than the rest of it, this situation compounds itself at increasing speed until a thin part of the filament either melts or becomes weak and breaks." Halogen bulbs last longer because the sublimated tungsten is converted to volatile halides, which then preferentially decompose back to elemental tungsten at the hot spots, healing them.