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1) In Microwave inner side there is strong metalbox, and there is a microwave generator called a magnetron. When you start cooking, the magnetron takes electricity from the power outlet and converts it into high-powered, 12cm(4.7inch) radiowaves.
2) The magnetron blasts these waves into the food compartment through a channel called a waveguide.
3) The foods it on naturntable, spinning slowly round, so the microwaves cook it evenly.
4) The microwaves bounce back and forth off the reflective metal walls of the food compartment, just like light bounces off a mirror. When the microwaves reach the food it self they don't simply bounce off Just as radiowaves can pass straight through the walls of your house, so microwaves penetrate inside the food. As they travel through it, they make the molecules inside it vibrate more fastly.
5) Vibrating molecules have heat so, the faster the molecules vibrate, the hotter the food becomes. Thus the microwaves pass their energy into the molecules in the food, rapidly heating it up.
I hope you understand these concept in simply and easily.
If you have any doubt or queries regarding to this concept, ask frequently we will happy to reply.