Instructions

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Additional studies: Spectral colours
A CD can be used as a mirror to look at the three LEDs. By
changing the angle to the correct position, the white LED will
be visible as stripes in all colours of the rainbow. The light
spectrum is pulled apart because the CD has narrow lines that
cause interference of the light waves. The lines of the red and
green LEDs are also pulled apart slightly, but contain only a
small part of the light spectrum.
The white LED is actually a blue LED. But apart from the LED
crystal there is fluorescent material, which activates the blue
light to radiate all other colours too. When the LED is off,
you can see the yellowish fluorescent material inside. The
material is similar to what is found in fluorescent tubes and
energy-saving lamps.