Planck Constant by Photocell

Abstract

This study presents the experimental measurement of Planck’s constant through photoelectric effect with a photocell. When monochromatic light of different wavelength is incident on a photosensitive surface, photoelectrons are emitted, and their maximum kinetic energy is measured through the stopping potential. By recording the stopping potential for different frequencies and plotting a linear graph, the slope is used to determine the value of Planck’s constant. The experimental results are consistent with Einstein's photoelectric equation, confirming that the maximum kinetic energy of the emitted photoelectrons depends on the frequency of the incident radiation rather than its intensity. The value of Planck's constant obtained from the experiment is in close agreement with the accepted value within the limits of experimental uncertainty. These findings provide strong experimental evidence for the quantum theory of light and support the concept that electromagnetic radiation is emitted and absorbed in discrete packets of energy, known as photons.