Microwave principle

The microwave oven works by bombarding the food placed inside the compartment with electromagnetic waves known as microwave. These waves make the food molecules vibrate at high speeds thereby producing heat that cooks the food.

Food contains molecules that act as dipole having positive and negative charges at opposite ends. When microwave is passed through the food materials the polar molecules present in the food tends to align themselves with the electric field but the electric field reverses at very high frequencies of 915 or 2450 million times per second. The molecules attempts to oscillate at such high frequencies generates intermolecular friction and causes food to heat.