The 1970s were filled with change. The Beatles broke up after over a decade creating magical music together. The Vietnam War ended. Apollo 13 returned to Earth. Jaws became the first blockbuster film to hit theaters. But perhaps the change from the '70s that affects our day-to-day lives the most today was manufacturing and mass distribution of the microwave oven. Over the years, it’s become a kitchen staple, an aid for lukewarm dinners and an ally to yesterday’s leftovers.

It’s more than that, though. Not only is it used for reheating, it’s also used for baking in small quantities, defrosting, roasting, blanching, boiling, and steaming. It heats and cooks food by the use of microwave radiation in the electromagnetic spectrum very quickly, but still maintains the nutrients in the food. But have you ever wondered why a microwave oven has a see-through window?

Spoiler alert: It’s not just for looking at your popcorn pop or to make sure your soup doesn’t bubble over. 

Microwaves [1] are a form of "electromagnetic" radiation; that is, they are waves of electrical and magnetic energy moving together through space. Electromagnetic radiation spans a broad spectrum from very long radio waves to very short gamma rays. Microwaves are produced inside the oven by an electron tube called a magnetron. The microwaves are reflected within the metal interior of the oven where they are absorbed by food. Microwaves cause water molecules in food to vibrate, producing heat that cooks the food. That's why foods that are high in water content, like fresh vegetables, can be cooked more quickly than other foods. The microwave energy is changed to heat as it is absorbed by food, and does not make food “radioactive” or “contaminated."

So where does the window come in? In this article, we’re going to get to the bottom of the front of a microwave. Why is that window there? Let’s take a closer look.

The Reason Why Microwave Ovens Have Mesh Doors

Microwaves are designed to keep in radiation, unlike, say, laptop computers. All microwaves are required to have two interlock systems independent from each other that stop the production of microwaves the second that the latch is released or the door is opened. These holes in the mesh door are substantially smaller than the penetration ability of the microwave’s sine waves, effectively keeping them locked within the confines of the oven. The microwave window isn’t just for show. It’s effectively keeping you safe from harmful waves. 

Light can pass through the perforated metal screen and glass window, but microwave radiation at the frequency of the oven is effectively blocked by the Faraday Shield effect. 

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What Are Faraday Shields and How Are They Keeping You Safe?

A Faraday Shield, or Faraday cage, prevents microwaves from penetrating through the oven. A Faraday cage creates a barrier between the internal components of a device and the external electric fields [2]. It works because an outside electric field causes a redistribution of the electric charges within the enclosure’s conducting material, which in turn cancels the field’s effect in the cage’s interior. This ensures that the electrical components within the enclosure can function properly without interruption. In layman’s terms, this prevents the microwaves inside the oven from leaking into the environment, which is something we want to keep as clean as possible.

How did this come to be? More than 100 years before the microwave was invented, physicist Michael Faraday built a container whose walls were of a conducting material that was intended to absorb and redistribute any external electrical field, so as to cancel the field’s effect upon the interior (and any contents therein) of the container [3]. This was discovered in 1836, by the way. Faraday never lived long enough to see the invention of the microwave (1946), but he can rest easy knowing how many households he’s touched.

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Buying Guide

• The door of a microwave is what stops the electromagnetic waves from entering your home. It’s what keeps you safe. So wouldn’t you want what you put in your microwave to be safe too?  The Gibson Soho Lounge Dinnerware set isn’t just microwave-safe. It’s also really cute. 

• The dishes are ceramic and durable and can be washed in a dishwasher. Now if you’re cooking leftovers, consider buying the Glasslock oven-safe container set. With these, you won’t have to worry about microwaving plastic. Faraday shields don’t help with chemicals melting into your food.

• If you’re like the rest of the world and shamelessly rely on your microwave, you know how messy it can get. Domestify sells the Eco Volcano Microwave Steam Cleaner. Fill it with water and vinegar, place it in the microwave for six minutes, and let it do its magic. When activated by heat, this unique microwave steam cleaner sprays eco-friendly disinfecting agents to loosen stuck-on messes so they easily wipe away with a sponge or towel, leaving your microwave cleaner than when you started.

• If you’ve noticed that the lighting in your microwave has dimmed, you should replace your bulbs at 1000Bulbs.com. This online light retailer sells bulbs for any microwave you own. And the best part is they come at a discounted price.

• And if you’re looking to replace your microwave with something as retro as its origin, Galanz sells the perfect cherry-red 700-watt countertop microwave for your Mad Men dreams.