This visually appealing device clearly illustrates the relationship between colour and wavelength. Seven coloured LEDs plus white, span the visible spectrum. Mounted in a robust vertical column, the LEDs can easily be viewed by a whole class. Depending on the diffraction grating used, first, second and third order fringes can be observed and used for calculations. The LED line has a rotary switch to allow users to select and measure the voltage across each individual LED. Knowing these voltages and the wavelength for each LED, Planck’s Constant can be determined. Students have a great opportunity to consider and minimize the sources of error in their experimental work.
- Demonstrates diffraction at different wavelengths
- Calculate the wavelength for each LED colour
- Measure the voltage across each LED and determine Planck’s Constant graphically