What is the principle behind a light bulb?

The principle behind a light bulb is that it converts electrical energy into light through resistance heating. In a light bulb, when electricity flows through the filament, the resistance of the filament material causes it to heat up. As the temperature of the filament rises, it reaches a point where it emits light. This phenomenon is known as incandescence. The design and materials of the bulb, such as tungsten for the filament and the glass enclosure to protect it, ensure efficient light production and durability. This process is fundamental to how traditional incandescent bulbs function, making option B the correct choice.