When something moves, it almost always has a wave pattern to its movement - this can be seen in water most easily, with ripples and ocean waves. A very common type of wave in the universe is electromagnetic waves. Light is an example of an electromagnetic wave, and so is a microwave. We can only see electromagnetic radiation in the visible light spectrum (which is why it's called the visible light spectrum), so microwaves are invisible.
Ovens[change | change source]
Microwave ovens work because microwaves make polar molecules (that is, molecules that act like tiny magnets) all face the same direction - to visualize it, imagine that the microwave oven is telling all of the molecules to face left. Then, the microwave oven reverses the waves, so that all of the molecules have to face the other direction - right, in this case.
Heat is just the movement of molecules, so when the microwave oven tells the molecules to turn left, then right, then left, over and over again, this makes them get hotter.
Water is the most common polar molecule in food, which is why dry foods don't tend to heat as well, or at all, in microwaves. Microwaves get absorbed by these polar molecules, but are ignored by non-polar molecules, and this is why microwaves can penetrate deep into certain kinds of food faster than regular heat. This is also why microwaves don't heat many plastics - those plastics that are non-polar get ignored, so the microwaves go straight through to the food.
Metals tend to spark in microwaves, rather than heating. The reason why is that metals like to give away electrons, so when the microwaves "push" at their magnet-like electrons, instead of turning, they just give the electrons away. A bunch of electrons running off on metal is called electricity, and we see it in the form of sparks.
How it works ?[change | change source]
A magnetron makes the radio waves in the oven. Apart from this the oven has a wave guide, turntable, and a timer switch. When we place the food inside the chamber and turn the timer switch on, it sends a command to the magnetron to send microwaves as well as to the turn table to start turning. The microwave can only heat food which has water molecules ( molecules are a small group of atoms stuck together by a chemical bond. Two atoms of Hydrogen and one atom of oxygen make water. H2o ). When the oven is started it sends microwaves. These waves go and touch the water molecules. Then the water molecules start vibrating against each other at a very high speed this generates heat. The turn table moves so that the food is heated evenly.
Only fine China Bone, Glass or special plastic materials can pass heat through them. Aluminium foil can not pass heat because when the waves come to it they reflect on it and go away. The microwave does not cook food but only heats it up from inside.