This apparatus is designed to determine the approximate value of Planck’s constant using the elbow voltage in the characteristic curves of a number of LEDs.
There are 7 LEDs covering from deep blue at 470 nm to near IR 940 nm mounted on the box with sockets for voltage and current measurements. By monitoring the voltage at which each LED just begins to emit light a graph of energy input as a function of light emitted frequency can be plotted and an approximate value of Planck's constant can be deduced.

External power supply for 9 volts is required or a 9 Volts battery with suitable connecting cords can also be used. Voltmeter (0-9 Volts), Ammeter (20mA) and 6 Banana Plug Connecting Leads also required.