Saw this on Engadget and I had to share.

The video gives a very detailed explanation on how G. L. Charvat visualizes the wavefront of his coffee can radar system. By using a feedback loop and tying it with red and green LEDs in opposite configurations, he’s able to visualize the rises and falls of the electromagnetic wave. He mentions that the frequency of this radar is 2.4 GHz, which corresponds to a wavelength of 0.125 meters, or 12.5 centimeters. Cool stuff.