Planck constant is a fundamental concept in physical sciences,and Millikan received the Noble Prize for determining it experimentallyin 1923. As the technology of solid state electronicdevices developed, an experiment was designed andadapted to determine the Planck’s constant using LED [1,2]. Herrmann and Sch¨atzle [3] questioned the validity of thisexperiment on the basis of the diode equation, and their approachwas further discussed by Morehouse [4]. In this article,the validity of this experiment is revisited.

Fermi energy, which is a theoretical concept, has been explored in an experiment for a copper wire in a Laboratory Course of Engineering Physics [1]. In this article, the scientific validity of this experiment is discussed and a method to determine Fermi energy is discussed.

De Broglie’s hypothesis of the dual nature of matter was confirmed experimentally independently by Davisson-Germer and G. P. Thomson. But most of the textbooks (e.g. [1]) discuss Davisson–Germer experiment. In this article, G. P. Thomson’s experiment of electron diffraction is discussed.