Demonstrating Helical Diffraction

By using a regular laser pointer and s spring from a pen or lighter, you can visualize helical diffraction analogous to what what can be seen on the famous Photo 51 taken by Rosaling Franklin. It was Photo 51 on which James Watson and Francis Crick based their model of DNA having an alpha helical structure.

I always wanted to make a video about this, but so far didn’t manage to. So for now, readers are referred to this excellent video of Steve Mould about it.