I have done an experiment to measure Planck's constant. I measured the activation voltage of the LED for each wavelength used. I calculated theoretical activation voltage results using the energy of photon emitted (E=hf) and V=E/e. The experimental activation voltage results were 50% lower than they should have been. This is not what I was expected because I thought that I would be seeing more light than one photon and therefore the activation voltage would be higher. I assume this has something to do with an energy gain in the system which was unaccounted for. Does this have something to do with an energy gain in the system to do with the depletion zone? Or something to do with the electrons increasing in energy as they move from the p-type material back to the electrical wire? I used a breaboard to wire the circuit
I wired the LED, a resistor and potentiometer to a breadboard which I then connected to a 2V battery. To measure the activation voltage I used a digital multimeter across the two ends of the LED. The experiment was conducted in a dark room. The potentiometer was turned until light was seen from the LED. At this point the voltage drop across the LED was recorded. I am trying to prove the value of Planck's constant. So far for red visible light, the activation voltage is 0.770V compared to calculated theoretical of 1.86V, orange of 0.895V compared to 2.02V, green of 1.111V compared to 2.3V, blue of 1.165V compared to 2.6V.