Five decades of determining Planck’s constant using light emitting diodes in Undergraduate Laboratories - A Review

Determination of Planck’s constant using LEDs has been a favourite experiment even from student perspective because of its simplicity and taught in undergraduate laboratories for the past five decades. Several modifications and improvements adopted in both experiment procedure as well as data analysis part of this experiment during this period have been revisited in this paper. From the simplest experiment to determine turn-on voltages using human judgement with naked eye to advanced equipment to detect even pico ampere current flowing through LED’s have been proposed by various researchers. Many of these proposals were successful in arriving at Planck’s constant with excellent agreement with standard value. Reasons for yielding unrealistic values of Planck’s constant have also been reported by several researchers.