Jefferson Lab's YouTube channel that includes a playlist titled Frostbite Theater. Since the last time that I watched Frostbite Theater the playlist has expanded to 68 videos. The videos offer short lessons on chemistry and physics topics.
One of the Jefferson Lab videos that I watched this evening is titled Measure the Speed of Light - With Chocolate! The three minute video is a demonstration of an experiment in which students use a chocolate bar and a microwave to attempt to measure the speed of light. As Jefferson Lab pointed out in the comments, the experiment could also be used to attempt to confirm the microwave's frequency. The video is embedded below.