Einstein postulated that light consists of a quantum of particles, called photon whose energy E is proportioned to the frequency n,by an equation, E = hn, where h is plancks constant. In this experiment,narrow band interference filters are used to select wave length, each filter selects precisely one spectral line from the light of a high pressure mercury lamp. The mono chromatic light falls on the cathode of the photocell. A capacitor, connected between cathode and anode of photocell, charged by anode,is used. Electro meter amplifier is used to measure the voltage at capacitor without current.