What is a photo cathode?

A photocathode is a type of material that emits electrons when it absorbs photons, typically in the context of photoelectric effect applications. It serves as a crucial component in devices like photomultiplier tubes and image intensifiers, converting light into an electrical signal. The efficiency and sensitivity of a photocathode depend on its material composition and the wavelength of incoming light. Common materials used for photocathodes include alkali metals and their compounds, which are effective at low light levels.