Definition
A material that emits electrons or changes its electrical properties when exposed to light. The electrical output (voltage, current, or resistance) varies with the intensity of the light striking the material, allowing it to be used as a sensor that converts light energy into an electrical signal.
Plain English
A substance that reacts to light by producing or changing electricity. Shine light on it and you get an electrical signal; the brighter the light, the stronger the response.
Context Anchor
Seen in aircraft electrical and instrument-system discussions, especially where light is used to trigger or control a circuit.
Derivation
From Greek 'photo' meaning light, and 'electric' from the Greek 'elektron' (originally meaning amber, which produced static charge when rubbed). So the word literally describes a material where light produces electricity.
Why Pilots Care
Many cockpit systems rely on photoelectric materials to work automatically, including instrument panel dimmers that adjust brightness to ambient cockpit light, and smoke or fire detectors in cargo compartments. Knowing the principle helps when troubleshooting why an automatic system isn't responding correctly.
Analogy
Think of it like a switch that light can operate. Instead of a finger pushing a button, light hitting the material causes an electrical response.
Intuition Check
Photoelectric does not mean related to taking pictures. Here, photo means light, and electric means the material creates or changes an electrical response when light hits it.
Example Sentence 1
The cargo compartment smoke detector uses a photoelectric material that triggers an alarm when smoke particles disrupt the light reaching the sensor.
Example Sentence 2
Maintenance confirmed the photoelectric material responded correctly to the test light.