Quantum Mechanics Experiments with Arduino

How to make experiments on the photoelectric effect with just LED’s and resistors.

Have you ever wondered how to perform an experiment in quantum mechanics? Do you think it requires complex equipment? Here you can find out how to perform an experiment on the photoelectric effect and how to measure Planck’s constant using readily available materials.

LED principles of operation

A light-emitting diode (LED) works like a diode. It acts like a hydraulic valve for water: a diode only allows the current to flow in one direction. Consider the following circuits:

A current flows in the left one, where, in principle, the diode appears as a perfect conductor, while it does not flow in the right one, where the diode appears as an open circuit (or, if you prefer, as a resistor of infinite resistance). The voltmeter on the left circuit shows almost a 5V voltage (a bit less, due to the small resistance offered by the LED when it allows the current flowing). The reading of the voltmeter on the right circuit is almost zero (not exactly zero, because the LED works as a resistor with a huge resistance).

An LED works the same way. The only difference with respect to an ordinary diode is that, when current flows, it…