Five (5) pieces having different surface areas Pd/n-GaP diodes were produced. Diodes were exposed by white fluorescence light lamb under different flux values. Electrical data values collected belonging to Schottky diodes; electrical parameters calculated using that data. Electrical capacitances of Schottky diodes have been obtained under different light flux. It is seen that electrical capacitances are remarkably changed with diode illuminated effective surface area and light flux.