Determining Planck’s constant with LEDs—what could possibly go wrong?

Abstract

Light emitting diodes have been used to determine Planck’s constant in introductory physics laboratories. One common method relies on the energy of the light emitted by the LED and its relation to the energy gap in the solid of which the diode is composed. However, there could be a problem with the data that are collected for this experiment. For some LEDs the energy of the light emitted from the LED can be quite different from the gap energy. If these LEDs are used for the experiment, the results will give different results for Planck’s constant.

Algorithm based determination of the Planck’s constant

“…This value was compared with the standard value of Planck's constant which is 6.62607 × 10 −34 J s. Hence, the Planck's constant was determined with accuracy by this method. Though we are still unable to find the accurate value of Planck's constant with a relative error less than 5%, this may be due to issues such as the non consideration of energy lost due to non radiative recombination and other issues as reported by Zollman and Bearden [15]. However, we are still able to find an accurate value of Planck's constant in comparison to the one which is currently been done in physics laboratory class.…”

“…Figure 2 shows the I-V curve for the four different colours of LEDs. The linear portion of the curve was extrapolated to find its intercept on the x-axis, which gives the turn on voltage (V o ) for the respective LEDs [15]. Even though the experiment is done in a complete dark room but we have avoided finding turn on voltage just by looking at the diode.…”

Using Arduino and online block-structured programing language for physics practical work

“…It also can introduce the quantum properties of solids to students. Furthermore, this experiment can be extended with more colours of LED for determining the Planck constant value [16].…”

First results using a Home-Kit designed in the COSID-20 project: teaching physics laboratory at a distance

“…In this section we discuss an experiment in which students combine electrical and optical measurements. This common experimental activity reported by several authors in several articles [17][18][19][20][21][22][23][24] is aimed at determining Planck's constant using light emitting diodes, a smartphone camera and low-cost equipment. The technique to measure the Planck's constant relies on the energy of the light emitted by the LED and its relation to the energy gap (Eg=eVg) between the conduction and valence bands of the semiconductor of which the diode is made of.…”