Definition
The property of certain materials that causes them to release electrons from their surface when struck by light. The amount of electron flow is proportional to the intensity of the light, allowing the material to be used as a light-sensitive electrical sensor.
Plain English
It is the ability of a material to give off tiny electrical particles when light hits it. The brighter the light, the more electricity it produces, so the material can act as a light detector.
Context Anchor
Seen in aircraft electrical and instrument discussions involving light-sensitive devices, such as photoelectric cells or sensors.
Derivation
From Greek 'photo-' meaning light, and 'emissivity' from Latin 'emittere' meaning to send out. Together: the ability to send out (electrons) in response to light.
Why Pilots Care
A pilot is unlikely to handle photoemissivity directly, but aircraft systems may use light-sensitive devices whose operation depends on this effect.
Grounding Statement
When light hits the right kind of surface, that surface can release electrons and create an electrical effect.
Intuition Check
Photoemissivity does not mean that a surface gives off light. Here, it means the surface gives off electrons because light hits it.
Example Sentence 1
The fire detection sensor relies on the photoemissivity of its sensing element to convert flickering flame light into an electrical signal.
Example Sentence 2
Materials with high photoemissivity were selected for the light-sensitive sensor in the early navigation instrument.