Planck’s constant determination from Ferry’s black-body radiation: a straightforward method

Abstract This article presents a simple and straightforward approach for determining Planck’s constant by examining the radiation emitted from a Ferry-like black body configured as a hemisphere. The Ferry black body was maintained at a constant temperature of ∼98.5 °C through the continuous flow of steam within a double-walled structure. The radiation emitted from the inner blackened surface and through a small aperture at the bottom was captured by a sensitive T-type double-junction thermocouple. One junction of the thermocouple was connected to a silver disc to capture the maximum radiations emitted from the aperture, while the other junction was maintained at room temperature in silicon oil. The variation in thermo-electromotive force (E.M.F.) across the double junction was recorded as a thermal sensing signal when the junction attached to the silver disc was exposed to the black body radiation. For calibration of the double junction, the second junction was heated in silicon oil while the silver disc junction was maintained at room temperature, and the thermo-E.M.F. was recorded as a function of temperature, which was measured using a mercury thermometer. The Planck’s constant obtained through this method was approximately 6.9 × 10 − 34 Js, which closely aligns with the standard value of ∼ 6.626 × 10 − 34 Js. The close correspondence between the measured and standard values of Planck’s constant confirms the effectiveness of this method.