The Complete Handbook of Light Bulbs

Chapter 1: Understanding Light Bulbs

A light bulb is a device that converts electrical energy into visible light. It seems simple—you screw it in, it comes on—but its mechanics, efficiency, and actual lifetime have enormous practical impact on operating cost, maintenance schedules, and the likelihood of a bulb failure at a critical moment.

To make good decisions about which bulb to install in a given fixture, you need to understand what is actually happening inside the bulb. Different technologies work in fundamentally different ways, and those differences determine not just how bright the bulb is or how long it lasts, but also what fixtures it will work in, how it behaves when dimmed, how much heat it produces, and whether it will shatter or fail safely.

How Light Is Produced

Light is produced by energy being released as visible radiation. There are several ways to do this.

Incandescent bulbs work by heating a metal filament (usually tungsten) to a high temperature—around 2700 to 2900 degrees Kelvin—until it glows. The filament is sealed inside a glass bulb filled with an inert gas (nitrogen and argon) or a small amount of halogen gas. As electrical current flows through the filament, it heats up and radiates light in all directions. The higher the temperature, the brighter the light and the whiter its color. This is a simple and ancient principle—the filament in an incandescent bulb works the same way as the glowing wire in a toaster. Incandescent bulbs typically last 750 to 2,500