Gas-discharge lamp

A lamp that produces light by passing an electric current through a gas or vapor. Its spectrum and operating behavior depend on the gas, pressure, and electrode design.

Electrical discharge: The flow of electric current through a medium, often accompanied by ionization and light emission. The lamp’s light begins when an electric field drives current through its gas.
Fluorescent lamp: A low-pressure mercury-vapor lamp whose ultraviolet output excites a fluorescent coating to produce visible light. It is a widely used low-pressure discharge design that relies on phosphor conversion.
Electric arc: A sustained electrical discharge through an ionized gas between electrodes. Many lamps maintain a bright arc between electrodes inside a sealed tube.
Incandescent lamp: A lamp that produces light by heating a filament until it glows. It generates light through heat rather than an electrical discharge in gas.
Plasma: An ionized gas containing free electrons and charged particles that respond collectively to electromagnetic fields. The conducting gas inside an operating lamp is a plasma.
High-intensity discharge lamp: A family of high-pressure arc lamps that produce intense light from a compact discharge tube. These lamps provide high output for street lighting, projectors, and large spaces.
Breakdown voltage: The minimum voltage required to make an insulating medium conduct through electrical breakdown. Starting a lamp requires enough voltage to initiate conduction in its gas.
Light-emitting diode: A semiconductor device that emits light when current passes through a p–n junction. LEDs use solid-state electroluminescence instead of ionized gas.
Excitation and relaxation: Processes in which atoms or molecules gain energy and later release it, often as photons. Collisions in the discharge excite atoms, whose relaxation produces characteristic light.
Neon lamp: A low-pressure gas-discharge lamp, commonly using neon, that emits light from an energized gas. Its colored glow makes the discharge itself visible in indicators and signs.

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