Calculating Planck’s Constant using LEDs

Submitted as final project for Mechanics.


This paper presents a method of measuring Planck’s constant using light emitting diodes (LEDs). An LED was connected to a variable power source and the voltage was gradually increased until the LED emitted light. From this threshold voltage, the voltage was steadily increased and both current and voltage were measured. Repeating this process with 5 different wavelengths of light yielded a value for Planck’s constant of 8.12 x 10-34 m2 kg s-1. The percent error was calculated to be .225 when compared to the known value of h, 6.626 x 10-34 m2 kg s-1. This error can be attributed to internal heating of the wires and the model of LEDs as resistors that follow Ohm’s Law.