Thing-a-day, Day 14: Double slit experiment

I’ve always wanted to try replicating this experiment, but I’ve never had a laser or the patience at the same time. I was frustrated with myself for not being able to adequately explain why its not possible to make a ‘dark’ light, which eventually lead to thinking about using interference to cancel out the light, which lead to this. I think the idea is that it’s not possible to use interference to cancel out light that is not coherent. Photo of the setup is here.

And here is a final geeky Valentine (you west-coasters still have 1/2 hour!)