What device converts electrical energy into light?

The light bulb is the correct answer because it is specifically designed to convert electrical energy into light. When an electric current passes through the filament of an incandescent light bulb, for example, the resistance of the filament causes it to heat up to a point where it emits visible light. This process is a direct conversion of electrical energy to light energy.

In contrast, other devices like a resistor generally dissipate electrical energy in the form of heat rather than converting it into light. Similarly, transistors are used for switching or amplifying electrical signals and do not produce light directly. Capacitors store electrical energy temporarily but do not convert it into light energy. Thus, the unique function of a light bulb in transforming electrical energy into light makes it the right choice for this question.