Photosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:Optical detectors, which are mostly quantum devices in which an individual photon produces a discrete effect.Chemical detectors, such as photographic plates, in which a silver halide molecule is split into an atom of metallic silver and a halogen atom. The photographic developer causes adjacent molecules to split similarly.Photoresistors or Light Dependent Resistors (LDR) which change… (More on Photodetector)