Basic Photoelectric Effect Demo!
The energy of a photon is dependent on the wavelength of its light. With this in mind, the minimum conducting voltage for two diodes of different wavelength (red and green) should be different. This can be used as a qualitative demo and a quantitative one for calculating Planck's constant (it gets the correct order of magnitude; about 30% accurate).
use the DC Power source on the 12 V setting. Hook a multimeter across the red diode first (it turns on first because it has larger wavelength), and record the voltage at which it turns on. do the same for the green diode. Planck's constant can be found by setting the photon energy and electric energy equal: q*V_conducting = hf = hc/(wavelength). Note to Co-Op Student: there is a PCB version under construction, and requires only a minor soldering job on the two LEDs, as the current soldering iron when this demo was made was terrible. When this is completed, remove this note and upload a photo.
Demo room information