Final answer:
An incandescent light bulb contains a tungsten filament that emits light due to resistance heating but becomes less efficient over time. Incandescent bulbs are less energy-efficient compared to LED lamps and CFLs. The light output diminishes as the bulb nears the end of its life due to filament degradation.
Step-by-step explanation:
An incandescent light bulb is a device consisting of a tungsten filament enclosed within a glass bulb that has been partially evacuated or filled with an inert gas. Electrical current passes through the filament, heating it to a high temperature. This heat causes the filament to glow, emitting both light and heat in the process. The light produced by this filament is due to the thermal radiation resulting from the resistance the filament offers to the passing electric current. However, as the bulb ages, the filament becomes thinner and may accumulate imperfections due to evaporation of the tungsten material, which can lead to a decrease in emitted light and eventual breakage.
Over time, the repeated heating and cooling of the filament can cause it to become brittle, altering its ability to efficiently produce light. The diminished light output late in the bulb's life is a sign of impending filament failure. Incandescent bulbs are known to be inefficient since much of the electrical energy is lost as heat rather than being converted to light.
In contrast to incandescent bulbs, energy-saving alternatives such as LED lamps (light-emitting diodes) and CFLs (compact fluorescent lamps) use significantly less energy to produce the same amount of luminous flux. When choosing between these different types of bulbs, it is important to compare their lumens to ensure equivalent brightness.