![]() In a fluorescent lamp, the emitted light is in the visible spectrum - the phosphor gives off white light we can see. This photon has less energy than the original photon, because some energy was lost as heat. When the electron falls back to its normal level, it releases energy in the form of another photon. When a photon hits a phosphor atom, one of the phosphor's electrons jumps to a higher energy level and the atom heats up. Phosphors are substances that give off light when they are exposed to light. This is where the tube's phosphor powder coating comes in. Our eyes don't register ultraviolet photons, so this sort of light needs to be converted into visible light to illuminate the lamp. ![]() The electrons in mercury atoms are arranged in such a way that they mostly release light photons in the ultraviolet wavelength range. When the electrons return to their original energy level, they release light photons.Īs we saw in the last section, the wavelength of a photon is determined by the particular electron arrangement in the atom. These collisions excite the atoms, bumping electrons up to higher energy levels. As electrons and charged atoms move through the tube, some of them will collide with the gaseous mercury atoms. This energy changes some of the mercury in the tube from a liquid to a gas. There is a considerable voltage across the electrodes, so electrons will migrate through the gas from one end of the tube to the other. When you turn the lamp on, the current flows through the electrical circuit to the electrodes. The electrical circuit, which we'll examine later, is hooked up to an alternating current (AC) supply. The tube has two electrodes, one at each end, which are wired to an electrical circuit. The tube also contains a phosphor powder, coated along the inside of the glass. ![]() The tube contains a small bit of mercury and an inert gas, typically argon, kept under very low pressure. The central element in a fluorescent lamp is a sealed glass tube.
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