How Do Microwaves Work

Whenever we cook or reheat food in microwave oven, we always wonder “How Do Microwaves Work?” Microwave ovens work by exciting the atoms which food is made up of. They are a form of electromagnetic radiation. 

For those of you more technically inclined they have a wavelength of 12.4 cm and an energy value of 2, 500 megahertz. They are the shortest form of radio waves.

How Do Microwaves Heat Food?

When radio waves hit any given substance they do one of three things: –

They are reflected. All metals reflect microwaves. This is important because it means that it’s possible to build a microwave oven that will keep the waves inside – you couldn’t, for instance, build one from glass. The down side, such that it is, is that you can’t put metal in the oven or run it on empty as the microwaves will crash into each other causing sparks and can damage the magnetron (the bit that produces the waves).

They are transmitted. Microwaves pass straight through glass, ceramics and most plastics. This makes them ideal containers for cooking in.

They are absorbed e.g. water, fats and sugars. When they are absorbed the waves cause the atoms within the substance to be excited (which means they move about faster) and this causes heat and the food to cook. This is why microwave ovens work!

Frequently Asked Questions

Why do I need to use a turntable to cook on?

Microwaves are emitted from one side of the oven only and although they do bounce around as they are reflected off the walls of the oven the food on the side nearest to the magnetron will be cooked more. Having the food turning around ensures it is cooked evenly.

Do microwaves work well on all types of food?

They work on all types of food but may not penetrate very thick bits. Bear in mind that they are absorbed by water, fats and sugars and cause these to heat. So food high in these ingredients will cook quicker.

Can I make a crust form on my food?

A crust is formed because of the heat in the air in a conventional oven. In a microwave the air is the same temperature as outside as air molecules aren’t affected by microwaves – this means no crust can form.
There are two ways to deal with this. One is to use a combination oven that enables crusts and browning or to microwave in a special cardboard sleeve.

Can the microwaves escape through the glass window

No! This is due to their size. Microwaves have a longer wavelength than visible light meaning they can’t get through the holes in the window whereas visible light can.

Does a microwave really cook from the inside out?

No this is a bit of a myth. With a conventional oven the food is heated from the outside in. When the outer layer warms up it warms the next layer and so on. The way microwave ovens work is to heat all the waters, fats and sugars at the same time. This means the food is cooked more consistently. But it’s all at the same time not from the inside out.

Should I use a lid when cooking in my microwave?

Lids are useful for two reasons – firstly to stop food splashing all over the oven and secondly to ensure that food is cooked thoroughly. The effect of a lid (it should be vented so do get a proper microwave one) is to build up heat in the form of steam under it. This helps kill bacteria.

Is it safe to heat baby food in a microwave?

Yes but be very careful about the temperature. The container you’re using won’t heat up much so it may feel that the food or milk inside is lukewarm when it could be very hot indeed. Always do a wrist test before feeding any heated food to your infant.

Is it best to use full power or a lower setting?

Microwave ovens work faster if you use a higher power setting but different foods need different settings. Larger items may cook more thoroughly on a slower power setting. There is some evidence that higher power settings may destroy some nutrients.

Is it really necessary to keep stirring the food during cooking?

Yes. It’s possible for microwaves to miss spots –usually because of different food items being present in the meal. Stirring as instructed ensures all the food is cooked well.

Why doesn’t the container heat up?

Because the microwaves are not absorbed but simply pass through and therefore have no effect on the container itself.

Wrapping up for how do microwaves work

Microwave ovens are the magical box that accelerate the process of cooking by invisible means. It works on the conduction from a flame. Microwaves spin inside the chamber and excite the water molecules in the food. This process results in cooking of food.

I hope this explanation of how do microwaves work has answered all your questions. If not please feel free to contact me and I’ll do my best to help.

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