Hello! I'm putting together ideas for "advanced" optics demonstrations/activities I'm giving in a few weeks, and want to tap into the creative brains here to see what your thoughts and suggestions are.

These are meant to be a step beyond basic undergraduate "here is a lens, look how it refracts light, wow!" demonstrations. Everyone participating has at least an undergraduate physics degree with some optics experience.

For example, participants will be asked to measure the speed of light using an array of equipment in front of them. The goal is to choose the long spool of fiber, two detectors, and a modulated source, measuring the time delay between signals at detectors before and after the spool.

I'm also going to do a Schlieren optics demonstration with a large parabolic mirror. Potentially also demonstrating how Kholer imaging techniques can eliminate ghost fringes in a free space system.

Beyond this, what else?