Physics Experiments to Inspire Undergraduates

PShardlow writes: I have recently been asked to propose two projects for a 1st year undergraduate teaching laboratory in the summer term this year. These are projects that a pair of students will spend 36 hours working on and as such can be quite in depth. A good project would include something they can build, something they can measure and something they can calculate. Previous projects have included: cloud chambers, a Jacobs ladder, a laser Doppler speed Camera, laser sound detection, smoke rings and physical random number generators to name but a few. This is an opportunity to really inspire students into the joy that can be experimental physics, but only if interesting projects are suggested by us demonstrators. So I ask the slashdot community for suggestions of fascinating projects to do, things that are relevant to today's physics problems but could feasibly be completed by a pair of first year undergraduates in 72 man hours? Any help will be much appreciated.