How does a photodiode function?

A photodiode functions by generating a current when it absorbs light. This is due to the photovoltaic effect, where photodiodes are designed to convert light energy into electrical energy. When photons strike the photodiode's semiconductor material, they can free electrons, allowing them to flow and create a current. This conversion makes photodiodes essential in applications such as light detection and communication systems.

The other options do not accurately describe the primary function of a photodiode. Emitting light when powered pertains more to devices like LEDs, which are designed specifically to emit light upon receiving electrical energy. Storing electrical energy is a characteristic of capacitors or batteries, not photodiodes. Similarly, amplifying sound signals is not relevant to the operation of a photodiode, as this action is associated with audio devices, such as microphones or amplifiers, but does not involve the light-sensitive properties of photodiodes.