Light Dependent Resistor 4.5mm Diameter MAX Dark Resistance - 20Mohms Resistance Max Power 100mW Spectral Peak - 560nm
A miniature low cost LDR in a miniature epoxy sealed open frame package (4.5mm dia.). Resistance reduces as light falling on the device increases.
Can a LDR be used as a switch?
The short answer is NO, not on its own.