Experimental Determination of Planck’s Constant Ryan Eagan The Pennsylvania State University University Park, Pennsylvania 16802 Email: ree5047@psu.edu July 25, 2011 Abstract Experimental determination of Planck’s constant h =6.626×10 -34 J · s is performed using Light Emitting Diodes (LEDs). Spectropho- tometry and basic circuit analysis techniques are employed to obtain empirical data with respect to the energy of the emitted photons of light and thus used to calculated Planck’s constant. It is found using three LEDs of different colors that the experimental value observed is 6.180 × 10 -34 J · s with a σ =3.092 × 10 -36 . 1 Introduction The origins of discrete packets of energy, or quantum, are a result of the work done by the German physicist Max Planck. Towards the end of the 19th century the classical theory of black body radiation was proving inad- equate as evident by what is know today as the ultraviolet catastrophe[1]. In October of 1900 Planck developed his black body formula, marking the true start of quantum theory. Planck’s original formula as publish was[2]: u(λ, T )= C 1 λ 5 ( 1 e C 2 /λT - 1 ) (1) where u is a function of frequency f and temperature T and h =6.626 × 10 -34 J · s is Planck’s constant and k =1.380 × 10 -23 J/K is Boltzmann’s constant, C 1 =8πch and C 2 = hc k . The success of Planck’s formula for black body radiation came from his concept that blackbody radiation was the product of submicroscopic oscillators that he referred to as resonators. The significance of this concept was that the mechanical frequency f of these 1