What is emitted by the photocathode when it is struck by light photons emitted by the input phosphor?

• A. Protons
• B. Neutrons
• C. Electrons
• D. Alpha particles

Answer: (C)

When light photons emitted by the input phosphor strike the photocathode, it causes the emission of electrons. This process is known as photoemission. In this context, the photocathode is designed to convert light into a corresponding electric signal for further processing in imaging systems like fluoroscopy.

The energy from the incoming light photons excites the electrons in the material of the photocathode, enabling them to overcome the work function of the material and be released into the vacuum. These emitted electrons are crucial in forming the image as they are then accelerated and focused by an electron optics system to create a visible output.

This transformation of light energy into electrical energy through the emission of electrons is fundamental in various imaging technologies, highlighting the importance of the photocathode's response to light.