Using the Light Sensor A LEGO light sensor utilizes a LED and a phototransistor to read the reflection of light off a surface. Light sensors are useful. - ppt download
Set of 5 Working LEGO Mindstorms Robotics 9V Light Sensor #2982c01 | eBay
Light Sensor Array for NXT or EV3
Lego Basics and More - Lego Mindstorms - Light Sensor Programming 1 (video 2 of 4) - YouTube