The light dependant resistor is an electronic component whose resistance decreases with increasing light intensity. It is also called as “Photo Resistor” or “Photo conductor”
The light dependant resistor uses high resistance semiconductor material.
When light falls on such a semiconductor the bound electrons [ ie., Valence electrons] get the light energy from the incident photos.
Due to this additional energy, these electrons become free and jump in to the conduction band. The electron –hole pairs are generated. Due to these charge carriers, the conductivity of the device increases, decreasing its resistivity.