Can you help me clear up the double slit experiment?

So I know what happens in a double slit experiment and that if you put an observer, it changes the outcome of the experiment. It has to do with Heisenberg's uncertainty, but how does his uncertainty principle apply to light? And if I were to recreate this experiment, how would I show that it changes based on observation if I was using a laser?

• The double slit experiment is not dependent on HUP. HUP would only come into play if you were interested in measuring both the position and momentum of the particles going through the slit. – Aaron Stevens May 23 at 18:15

To make things even more cool you can then put, after the slits, a polarizer at $$45^\circ$$: this is a 'quantum eraser': it removes the information you gained from adding the vertical & horizontal polarisers. And the interference pattern then comes back.