This is a very small light sensor. A photocell changes (also called a photodetector, CdS or photoconductive cell) resistance depending on the amount of light it is exposed to. These little sensors make great ambient light triggers (when light in the room turns on, do something) and for interesting projects with your Raspberry Pi!Light resistance : ~1k OhmDark resistance : ~10k OhmMax voltage : 150VMax power: 100mW* 2 x 4 x 5mm4mm between pins31mm lead length