The reflectivity of infrared light varies with the color and distance of the reflecting surface. According to this principle, Grove - Infrared Reflective Sensor utilizes a RPR220 reflective photosensor module to detect color and distance. When a light-colored object approaches,the signal intensity received by infrared reflective sensor increases and the indicator LED on board turns red. When a dark-colored object approaches, the intensity decreases and the LED turns off. 

 

This sensor is a basic and widely used part in applications such as line-following cars, rotary speed detection, auto data logging on utility meters or other situations where color or distance contrast is sharp.