What happens when visible light hits the photocathode?

When visible light hits the photocathode, it converts into electrons. This is a crucial process in various imaging technologies, particularly in fluoroscopy and other applications involving photomultiplier tubes or image intensifiers.

The photocathode is specially designed to respond to light by emitting electrons through the photoelectric effect. When photons from visible light strike the photocathode's surface, they transfer their energy to the electrons. If the energy is sufficient, these electrons are freed from the material and emitted into the surrounding vacuum or gas in a photomultiplier tube.

This conversion process is fundamental to creating an electronic signal that can be further amplified and used to form an image or to visualize motion in real time, making it essential for applications in areas such as medical imaging and radiation therapy. The efficiency of this conversion is one of the factors that influence the overall performance of imaging systems.