Abstract: The wavelength dependence of saturation photocurrents in the experiment of photoelectric effect is investigated under the condition of equal photo number. Our results indicate that the saturation photocurrents are determined almost only by the wavelength of incident light and represent the photoelectric efficiency of cathode material. The theoretical formula of achieving the condition of equal photon number is derived on the base of the quantum nature of light,which is in agreement with the experimental results.

Key words: photoelectric effect, saturation photocurrent, photo number, light intensity, photoelectric efficiency