Let's set the record straight. This first video is a clever hoax. It is not possible to pop popcorn using cell phones. See how it's done in the second video.
The second video explains how you could duplicate the hoax by placing the magnetron from a microwave oven underneath the table where the magic cell phone sleight of hand is taking place. I would not try this at home by the way, because exposure to a 1000-watt microwave emitter might not be healthy.
Herein is the crux of the matter. Yes, it is true that both microwave ovens and cell phones emit radiation in the microwave frequency range. Yes, it is true that microwaves can heat up materials that contain water molecules. (The oscillating electromagnetic fields in the microwaves interact with the dipolar water molecules, causing them to rotate. The rotations result in frictional heating as the molecules jostle each other.) And obviously it is true that you can use a microwave oven to heat up and pop your corn.
However, logic and simple principles of physics dictate that you can't do this with a couple of cell phones. Why? Because the signals don't contain sufficient energy! Cell phones operate at a power of around one watt, while microwave ovens are around a thousand times as powerful. How long does it take to cook even a few kernels of popcorn in the microwave? Well, I took three kernels, placed them in a microwave oven, and set the oven to maximum. It took over a minute to pop them. Now making a rough estimate, assuming you could channel most of the energy emitted from a cell phone into a kernel of popcorn (much will be radiated away), and assuming the heat isn't dissipated faster than the energy is absorbed, how long would it take to pop? We estimate somewhere in the neighborhood of at least ten hours!
Achtung! The second video demonstrates one way of duplicating the hoax by placing the magnetron from a microwave oven underneath the table where the magic cell phone sleight of hand is taking place. HOWEVER THIS IS QUITE DANGEROUS. DO NOT TRY THIS AT HOME. Exposure to a 1000 W microwave emitter is hazardous and you can electrocute yourself by fiddling with the wiring in the microwave.
Adam Weiner is the author of Don't Try This at Home! The Physics of Hollywood Movies.