If you want to impress your friends with a nifty, easy to conduct experiment, you’re going to need a normal incandescent bulb (‘a bulb’ as old people would say), a compact florescent bulb and a CD.

Hold the CD near the normal bulb and look at the colour spectrum – you can see the full rainbow, dancing across the surface. Then repeat over the CFL. What you see is a three distinct bands of colour – red, green and blue. It’s a nice party trick and spreads lots of FUD about the blasted things.

The next experiment is a bit trickier because it requires you to have a big enough room to do it in, and it needs to be painted the same colour all the way, light one half with a normal bulb and one half with a CFL, then just compare the way the walls look.

Really couldn’t be simpler.