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How Do Microwaves Work?

silver microwave oven

When you put food in the microwave, it comes out hot in a matter of minutes or seconds, seemingly by magic. But what happens to your food while it’s spinning around in there?

Many cooking methods involve a visible heat source, so microwave ovens can seem mysterious by comparison. You can’t see anything happening, yet your food still comes out hot. Let’s take a look at what goes on inside your microwave!

What Are Microwaves?

Today, “microwave” is what you might call a small, box-shaped cooking device in your home. However, that device’s full name is actually “microwave oven” because it uses a heating method called microwaves. For the rest of this article, we’ll use “microwave” to refer to the heating method, and “microwave oven” to refer to the appliance.

Microwaves are a type of energy that you can’t see. They’re part of the electromagnetic spectrum: the full range of electromagnetic radiation arranged in order of wavelength. Many other things you’re familiar with are also on this spectrum, such as visible light and X-rays.

On the electromagnetic spectrum, microwaves fall between infrared waves and radio waves.

How Do Microwaves Cook Food?

Microwaves are the right wavelength to be absorbed by food, so they’re ideal for cooking. A microwave oven is designed to create and contain microwaves, so they can interact with what you put inside, causing it to heat up.

Your microwave oven has a part called a magnetron. The name may sound like a sci-fi weapon, but it actually produces microwaves using electricity. Inside a microwave oven, microwaves generated by the magnetron bounce around and into your food. The sound a microwave oven makes comes from the fan that cools the magnetron, and from the hum of the electrical components at work.

The mesh that you see on your microwave oven door traps the microwaves inside, while letting you watch the cooking process. It works because the holes in the mesh are smaller than microwaves but big enough to let visible light waves through.

The frequency of microwaves lets them get absorbed by fat, water, and sugar, which is how they cook and heat food. Microwaves trigger friction between water molecules, which results in heat.

Because microwaves penetrate food so well, microwave ovens can heat and cook things much faster than a conventional oven. However, microwave ovens don’t produce the hot air needed to create crispy skins and crusts, which is why they’re not ideal for heating things like pizza.

Also, while microwaves heat food quickly, they don’t do it very evenly. That’s why your microwave oven may have a spinning plate to move the food around, so every part gets some heat.

Are Microwave Ovens Safe?

Because microwaves are a type of radiation, some people worry about using them for cooking. However, that’s because people often think “nuclear” when they think “radiation.” In truth, many harmless things, like visible light, are also types of electromagnetic radiation.

Microwaves aren’t nearly as harmful as nuclear radiation. Still, you wouldn’t want to be exposed to them at high levels. They would heat the water in your body just like they heat the water in food, causing burns.

Luckily, the mesh in your microwave oven door traps the microwaves inside, so they can’t get out of the box. Unless your microwave oven door is damaged (in which case you should replace the whole thing), these appliances are safe to use.

That said, putting the wrong thing in a perfectly-functioning microwave oven can make it dangerous. For example, a fork or a piece of foil will spark if heated by microwaves. Certain types of plastic will melt in a microwave oven. And if you overheat things, you could burn yourself when you take them out.

To keep microwave ovens safe, you should always follow the instructions for both the appliance and anything you put in it.

Not only are microwave ovens safe when appropriately used, but they’re great at preserving nutrients in food, making them one of the healthiest cooking methods. Because microwave ovens work so fast, there’s less time for the heat to deplete nutrients.

Of course, unhealthy food cooked via microwaves will still be unhealthy. But microwave ovens are great at preserving the nutrients in things like vegetables. They’re also an energy-efficient cooking method since they can cook something very quickly.

The microwave oven might seem like a simple appliance, but it has made a vast difference in how quickly and easily we can cook food. Now that you know how it works, using a microwave oven may seem a little less like magic—but with fast, safe, nutritious results, it’s still pretty amazing.

Elyse Hauser Elyse Hauser
Elyse Hauser is a Seattle-based writer and editor with a Master's in Writing Studies from Saint Joseph's University. Her work has appeared in publications like Racked, Vine Leaves Literary Journal, and Rum Punch Press. She was awarded a 2017 Writing Between the Vines residency.  Read Full Bio »