Having access to a warm meal is important and technology allows us to even heat our own food on the go. Even so, almost every household and even some workplaces have a microwave for people to quickly warm their meals. But do you know how they work? Microwaves are actually a type of electromagnetic energy similar to visible light but work at a higher frequency.
The invention of the microwave
The microwave was invented by accident in 1945 by a man called Percy Spencer who worked for the company, Raytheon. He was testing a new vacuum tube, a magnetron, for a radar. While working on it, he noticed that the snack he had in his pocket had melted. Realizing that the microwaves may be responsible, he decided to test it out again with an egg. He placed one inside the box still in its shell and it exploded on his face.
Percy now knew he had discovered a way in which to cook food in seconds. The next time around, he placed some popcorn kernels inside. They began popping away almost immediately and he was able to share it with his coworkers, which solidified the invention of the microwave.
On this day in 1945, Percy Spencer filed a patent for a microwave cooking oven (October 8, 1945). pic.twitter.com/R8ZYxFOcGc
— Vala Afshar (@ValaAfshar) October 8, 2017
How does it work?
A microwave oven has an electron tube called a magnetron that generates short radio waves. When electrical energy is pumped into it, the apparatus will start to resonate. It will then produce electromagnetic waves. Inside the magnetron is a solid metal rod known as a cathode. This is surrounded by an anode. Once the magnetron is switched on the cathode heats up and electrons start to “boil” off it. The electrons will very quickly move across toward the anode which has little holes cut into it called resonant cavities.
A powerful magnet is placed underneath the cathode which causes the electrons to move around in a circle between the cathode and the anode. This causes the cavities to resonate and emit microwave radiation. Radiation is then channeled through a waveguide to cook your food. The food begins to cook when the microwaves reflect back and forth in the metal oven, causing the water and fat molecules in the food to vibrate. These molecules heat up and the food cooks.
Trivia: THE CAVITY MAGNETRON from 1937 ⚡️
Cavity Magnetrons were part of the radar systems used to detect approaching enemy aircraft. The electromagnetic waves it produced could also heat food, an accidental discovery which led to he invention of the microwave oven. pic.twitter.com/rFQaBhXiHX
— 🅼🅾🆃🅾🆃🅸🅽🅶🅻🅴 🏍 (@mototingle) April 22, 2023
Microwave ovens contain a solid Faraday cage on five of their sides and a mesh Faraday cage on the door. This cage prevents any electromagnetic waves from escaping and protects the user from microwave radiation.
While there’s a story about the microwave involved in reanimating frozen hamsters, it’s not necessarily its origin. It’s worth mentioning that James Lovelock did defrost cryogenically frozen hamsters using the same technology. However, this didn’t happen until the mid-50s. He also did an experiment by cooking a potato in a microwave oven, so in my opinion, he deserves some recognition.
Aside from ovens though, Percy was working on magnetrons as part of testing radars. Today, they are used in satellite communications, Bluetooth, Wi-Fi, phones, navigational equipment, and medical procedures. Maybe one day, technology will advance far enough for us to defrost cryogenically frozen humans.
Photo credits: The feature image is symbolic and has been taken by Jaroslav Moravčík.
Sources: Steven Tweedie (Insider) / Chris Woodford (Explain That Stuff) / Matt Blitz (Popular Mechanics) / Derya Ozdemir (Interesting Engineering) / Rhona Shennan (NationalWorld)