Inverse Square Law Using Photocell
Inverse Square Law Using Photocell
Object:- To verify Inverse square law of light using a photocell.
Apparatus Required:- Optical bench, Photocell housed with Red and Black sockets, lamp house with lamps, DC Microammeter.
Theory:- The Photoelectric emission may be regarded as a phenomena of liberation of an electron at the surface of a metal when a photon of light having energy above threshold energy (metal work function) incident on a metallic surface and transfer the enough energy to the electron to escape through the potential barrier layer. The photo cell can be considered as the generation of a voltage across a circuit element under illumination. Let P be the illuminating Power of a source so the intensity of illumination I due to it at a distance r would be I= P/r2 Since the photo electric current (?p) produced is directly proportional to the intensity of illumination ie. I a ?p I=K?p Where K is constant, hence I= P/r2 = K?p. Since P and K are constant hence the relationship between 1/r2 and ?p is straight line which verifies the inverse square law of radiation.
