Definition
A semiconductor diode whose electrical conductivity changes when light strikes it. When light falls on the junction of the diode, it generates a small current or alters the current already flowing through it, allowing the device to act as a light-operated electronic switch or sensor.
Plain English
A small electronic part that reacts to light. When light hits it, it lets electricity flow differently, so it can be used to detect light or turn something on and off based on whether light is present.
Context Anchor
Seen in aircraft electrical and avionics discussions, especially in circuits that sense light for automatic dimming, warning systems, or other light-based controls.
Derivation
From 'light-sensitive' (responding to light) and 'diode' — from the Greek 'di' (two) and 'hodos' (path or way), meaning a component with two electrical paths that allows current to flow mainly in one direction. The name simply describes what it is: a two-terminal device whose behavior is changed by light.
Why Pilots Care
Light-sensitive diodes are used in automatic dimming circuits for cockpit instruments and in sensors that feed information to avionics. Knowing the term helps when reading system descriptions or troubleshooting guides.
Intuition Check
Do not confuse a light-sensitive diode with a light-emitting diode. A light-sensitive diode detects light; a light-emitting diode produces light.
Example Sentence 1
The cockpit's automatic instrument dimming system uses a light-sensitive diode to detect ambient brightness and adjust the panel lights accordingly.
Example Sentence 2
During preflight, the technician checked the light-sensitive diode in the sensor unit to ensure it responded correctly to ambient light.