A Century of Planck Constant Measurement

M. Goswami and S. Sahoo

NIT Durgapur

The Planck constant ‘h’ is a fundamental physical constant which plays an important role in understanding the behaviour of matter at the subatomic level. It is a cornerstone of the theory of quantum mechanics, which links wave-like and particle –like properties. Although the first numerical estimate of h was given by Planck himself, the American Physicist R. A. Millikan measured its value first time using the photoelectric effect in 1914. That is why the year 2014 is considered as centenary of Planck constant measurement. The measurement of the Planck constant, h, is now entering a new phase as its importance has been linked to a proposed redefinition of a kilogram unit of mass. In this article, we briefly review on measurements of Planck constant.