How do incandescent lightbulbs emit light?

How do incandescent lightbulbs emit light?

• A. They emit light by causing a solid object to heat up so that it glows
• B. They emit light by chemical luminescence in a gas
• C. They rely on phosphorescent coatings
• D. They rely on external energy to excite a phosphor

Answer: (A)

Incandescent bulbs emit light through incandescence: heating a solid until it glows. In these bulbs, electric current passes through a tungsten filament. The filament’s resistance turns electrical energy into heat, and when it gets very hot, it emits visible light as part of blackbody radiation. This produces a broad spectrum of light with a warm color. The other ideas describe different lighting methods: chemical luminescence in a gas would rely on chemical energy or ionized gas, phosphorescent coatings store and later re-emit light, and exciting a phosphor with external energy is how fluorescent or LED-based lighting works, not a hot filament.

Incandescent bulbs emit light through incandescence: heating a solid until it glows. In these bulbs, electric current passes through a tungsten filament. The filament’s resistance turns electrical energy into heat, and when it gets very hot, it emits visible light as part of blackbody radiation. This produces a broad spectrum of light with a warm color. The other ideas describe different lighting methods: chemical luminescence in a gas would rely on chemical energy or ionized gas, phosphorescent coatings store and later re-emit light, and exciting a phosphor with external energy is how fluorescent or LED-based lighting works, not a hot filament.