The Experiment

If you have a way to vary voltage (0 to about 4 volts D.C.) on LEDs which emit light of different colors, you can do the experiments and calculate h.

If you do not have the apparatus, you can determine Planck’s Constant in two ways:

• Click here to see our graphs of light intensity versus voltage.
• Go to Radio Shack’s catalog and look up wavelengths and threshold voltage for their LEDs.