Plank’s Constant Apparatus using LED

Description

The apparatus uses a set of LEDs of various colors (such as red, green, blue) with known emission wavelengths.

A variable DC power supply and series resistors control the voltage and current supplied to each LED.

Measurement devices like digital voltmeters and milli-ammeters are connected to accurately record the voltage at which each LED begins to emit light (threshold voltage).

The experimental data allow plotting of the voltage against the reciprocal wavelength of the LEDs to calculate Planck's constant using the relation:

V

=

h

c

e

λ

V=

eλ

hc

The setup often includes a viewing pipe to reduce ambient light interference and improve measurement accuracy.

This apparatus is widely used in physics and electronics labs to provide a hands-on understanding of quantum theory, photon energy, and the photoelectric effect by practical estimation of Planck’s constant based on LED emission properties.