How to measure Planck’s constant using an LED
- Measure LED threshold voltage using voltmeter and ammeter.
- LED converts electron energy to photons. Energy lost by electron = energy gained by photon = (electron charge) times (voltage).
- So, if threshold voltage is 2.2 volts, energy of emitted photon must be 2.2 eV.
- Use E=hc/lambda, and measure lambda using Red Tide spectrometer with Logger Pro (see below pic), to determine h. Take data using LEDs of 4 different colors and fit data to line with slope h.
- Hand held spectrometer can be used to view LED spectrum.