photosensor
nounUK /ˈfəʊtəʊˌsɛnsə/
US /ˈfoʊtoʊˌsɛnsər/
A photosensor is a small part that can tell when light is there.
The night-light turns on because its photosensor feels the room getting dark.
RELATED WORDS
OTHER MEANINGS
2. A device that changes light into an electrical signal.
The engineer used a photosensor to measure how bright the lamp was.
3. A part in machines that helps them notice light or darkness.
The robot's photosensor helped it follow the bright line on the floor.
4. A component used in cameras and phones to adjust to different lighting.
Your phone screen gets brighter thanks to a tiny photosensor near the speaker.