Everything you didn’t ask to know about: Microwave ovens

A Journey into Microwave Physics

The microwave oven transforms frozen dinners into edible delights in minutes. They are a convenient and safe tool when used properly, but how do they work?

Microwaves are safeMany of us hear the term ‘radiation’ and get nervous, but radiation simply refers to the transfer of energy from one place to another.

Microwave “radiation” is non-ionising, meaning it heats things up. It’s similar to the energy or ‘heat’ transferred from sunlight, radios and signals from mobile phones.

Microwaves can preserve the nutrients in your foodPopcorn was the first food cooked in a microwave oven by its inventor Percy Spencer in 1945. The second item was an egg that exploded - and may be where the term 'egg on your face' comes from!

Studies have shown that microwaving doesn't have a negative impact on nutrient levels compared to other cooking methods. Not only won’t your microwave turn your burrito radioactive, it can sometimes even help preserve certain vitamins as it cooks food quickly, minimising nutrient loss from prolonged heat exposure.

The science behind the applianceImagine a microwave oven as a cosmic dance floor where unseen forces collide and interact.

At the centre of this molecular mayhem sits the ‘magnetron’, a culinary conductor generating waves of energy. These invisible waves bounce around the oven's cavity ready to interact with any unsuspecting food morsels. Microwaves work best at heating 'moist' foods by creating friction, and so heat, between the water molecules in the food.

The mystery of the rotating trayThe rotating tray inside acts as a molecular choreographer, ensuring that each food particle has an equal opportunity to interact with the microwave's energy waves. This constant movement prevents the formation of hot and cold spots.

The tray also provides a stable platform, preventing the food from flying all over the place. It's like a personal chef guiding each morsel through a culinary symphony, ensuring that everything is cooked to perfection.

The hot and cold spot paradoxAnd a bonus life hack – if you notice that there are some cold spots when you heat food in a microwave, it’s because the centre of the tray is the only spot that doesn’t move when the plate rotates. So when you put your food in, keep it near the edge for the best results.

But remember to always wear safety goggles when using a microwave, just in case the tray decides to break into a spontaneous disco routine (jk).

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Sources:

Editors of Encyclopaedia Britannica (2020). Microwave oven | Britannica. In: Encyclopædia Britannica. Available at: https://www.britannica.com/technology/microwave-oven.

‌Gallawa, John Carlton (1998). "The History of the Microwave Oven". Archived from the original on 9 July 2011. Available at: https://web.archive.org/web/20110709081022/http://www.gallawa.com/microtech/history.html