lightsensor
nounUK /ˈlaɪt ˌsɛnsə/
US /ˈlaɪt ˌsɛnsər/
A light sensor is a small part that tells how bright or dark it is.
The night-light turns on by itself because it has a light sensor.
RELATED WORDS
OTHER MEANINGS
2. A device in a phone that makes the screen dimmer or brighter.
My phone's light sensor made the screen brighter when I went outside.
3. A part in a robot that helps it follow a line or avoid dark spots.
The robot used its light sensor to stay on the white track.
4. A gadget that turns streetlights on when the sky gets dark.
The streetlight's light sensor switched it on at sunset.