Planck’s Constant

Item Code: SN627

Principle and Working:

The photon energy by Einstein equation E=hv is equal to energy gap Eg between the valence and conduction bands. The energy Eg is equal to the energy barrier eV0, that electron have to overcome in going from n-doped side of diode junction to p-doped side when no external voltage V is applied to the diode.
In the p-doped side, electron recombine with holes releasing the energy Eg in the form of photon emit given by equation
Eg = eV0




  • Compact design
  • stand alone unit.
  • Dual purpose (Voltage and Current) 7 segment display.
  • Linear control over light intensity.
  • Different wavelength filters.

  • To determine planck’s constant.
  • To verify the inverse square law.

  • Plank constant : Tungsten-halogen bulb 12V / 35W Scale Length 400mm, Photocell Cs Vacuum Photo tube, Dark-current < 0.003 µA, Display mode switch to displays current (m A) or voltage (V), Current multiplier X1, X0.1, X0.01 & X0.001, Accelerate Voltage -15V to 0V & 0 to15V, < ±2%, Power supply 220V / 50Hz, Measuring error < ± 15% compared with the recognized value (h=6.62619x 10-34 J.S)
  • Set of colour filter : Red 635nm, Orange 570nm, Yellow 540nm, Green 500nm, Blue 460nm
  • 1 Planck’s constant apparatus
  • Set of 5 different wavelength filter.
  • 1 Screw driver