1. a cathode that emits electrons when struck by photons of light, used in photoelectric devices and image sensors.
Usage: technical; physics

Examples

• The photocathode in the photomultiplier tube converts incoming light into electrical signals.
• Modern image sensors use photocathodes to detect and measure light intensity.
• The sensitivity of a photocathode depends on the material and wavelength of incident light.
• Researchers selected a cesium photocathode for its high quantum efficiency in the ultraviolet range.
• The photocathode must be maintained in a vacuum to prevent oxidation and preserve its electron-emitting properties.