Photo Conductive cellPhoto conductive switch is a that transducer which conductivity is directly proportional to solar radiation. or it convert solar radiation into conductivity .
In these various type material are used
Photo conductive material is convert in form of photo conductive switch by help of ceramic base. For safety purpose a glass window is also covered above it.
Photo cell is combined form of conductive switch and electric source.
In night period will not got sun light so conductivity will less so contact will also open. RElay being discharged and NC contact is closed so light being ON.