photocell
/ˈfoʊtoʊˌsɛl/
noun
- An electronic device that changes light energy into electrical energy, often used in automatic lights, solar panels, and light meters.
- Solar garden lights use a small photocell to charge during the day and glow at night.
- The streetlights turn on automatically when the photocell detects darkness.
- A photocell in the camera measures the light and adjusts the exposure.