Planck’s Constant Apparatus is designed to study the Photoelectric Effect and to obtain Planck's constant. The Main Unit of the Instrument comprises an inbuilt regulated power supply, two digital meters for voltage and current measurement on the front panel, a vacuum-type photo cell enclosed in a metal box, and a halogen source provides light energy to the photo cell or photo vacuum tube. A filter is placed between the light source and photo cell to select different wavelengths. The different filters produce different wavelengths. Terminals are provided on the front panel to make connections externally with the help of connecting leads. Complete in all respects.

To determine the value of Planck’s constant using a photoelectric effect

The photoelectric effect refers to the release of electrons from a material’s surface when it absorbs energy from incident light. Each metal has a specific minimum binding energy required to free an electron, known as its work function, which is a unique property of that element. When a photon strikes a bound electron, it transfers its energy to the electron. If the photon’s energy is less than the metal’s work function, it is re-emitted without ejecting any electrons. However, if the photon’s energy exceeds the binding energy, the electron is emitted with kinetic energy equal to the difference between the photon’s energy and the work function. The stopping potential is determined by adjusting the anode voltage until the photocurrent drops to zero. By plotting stopping potential against light frequency, the slope of the graph provides the ratio h/e, which allows calculation of Planck’s constant (h) and the material’s work function. This apparatus also helps students develop a fundamental understanding of the quantum nature of light.