Light-Spectra

The audience is given little cardboard discs that are equipped with a special grid foil. If you look at a light source through the foil, you can see many rainbows.
If an incandescent light bulb is viewed, a continuous spectra appears. However, if you look at an energy saving light bulb the rainbow effect consists of many separate coloured parts

How does it work?
Diffraction takes place through the very thin lines of the grid. This causes the incoming light to separate into all its constituent colours; we call this a spectrum.
The emission spectrum from an energy saving light bulb is different from the spectrum of an incandescent light bulb, as the former only emits light within certain frequency ranges. The “normal” light bulb, however, emits light in all frequencies (i.e. in all colours) of visible light.