Lightening like reaction caused in microwave while cooking in aluminum...?

Question

I was cooking food in aluminium in the microwave and about 20 seconds in, there was some kind of flash, why did this happen? I stopped the microwave and took out the aluminium and I'm curious as to why it happened...

Answer 1

Microwaves are short radio waves. Waves can be transmitted as through glass or plastic, absorbed and changed to heat as in food and reflected as from the aluminum foil or the insides walls of the oven, being metal. They can be reflected back into the magnetron, which generates the waves and can cause damage. The arcing you see is the buildup of charge similar to lightning.

Answer 2

When the strong microwaves produced by a microwave oven interact with a sheet of aluminum foil, their electric fields cause the mobile electrons in the foil to accumulate at the sheet's sharp, pointed tips. This build-up of electrons creates a strong electric field in the surrounding air. When the electric field becomes strong enough it causes free electrons in the air to accelerate and jar loose more electrons from gas molecules in the air, which then go on to jar even more electrons loose. This chain reaction creates an electrical charge in the air, which shows itself as sparks.

Answer 3

First of all you don't put a metal inside a microwave. That's because it'll cause sparking.

Actually microwaves heat by giving radiation (of microwave region) which leads to a flow of charge (as explained above) which causes heating of the particles.

This phenomena is similar to lightning as lightning is also nothing but extreme charge which ionizes air particles and heats the surrounding air.