Lascells Planck's Constant

A selection of LEDs cover the range from deep blue to infra-red. 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 deduced.
The system is an excellent illustration of modern electronics and gives a good investigation into a difficult topic in Post-16 physics.
The LEDs are mounted in a self-contained box with voltage control and monitoring points for current and voltage. A protection resistor is included to prevent damage to the LEDs.
Complete with viewing tube but requires a 5V d.c. lab. power supply.