How do Microwave Ovens “actually” work?
Hey friends, Happy Wednesday!
I always send out my emails at 8 am EST on Wednesdays. I’m 6 hours late today, sorry! But I'm pretty sure your experience with microwave ovens won't be the same after reading this issue :)
Answer to the question I posed last week
Last week, we discussed Radars and asked if you could think of other uses for Radars apart from the ones I mentioned. It is also used to map the surface of the earth from space; and track insects and birds in the atmosphere.
Let’s look at how a Microwave Oven “actually” works this week. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for food, etc. Let's jump in!
Tweet of the week
I’m sharing a cool fact about gadgets on Twitter. And here is one of them for you
How do Microwave ovens work?
History
An American physicist, Percy Spencer had a candy bar in his pocket while experimenting on radars when he switched on the magnetron. To his surprise, the bar quickly melted because of the heat the magnetron generated. This gave him the idea that a magnetron might be used to cook food.
How are microwaves produced?
Microwave ovens use a device called Magnetron which converts electricity into microwaves. These waves are then channeled through a waveguide on one side of the oven. Microwaves are electromagnetic radiation similar to visible light, but cannot be seen with the naked eye and are harmful to human cells and tissues. That’s the reason the microwave oven has a solid metal box reflecting the waves within the oven.
Figure 1: Electromagnetic spectrum
Why only Microwaves?
The wavelength of microwaves used in an oven is about 12 cm. Any type of radiation with a longer wavelength passes through the food. A shorter wavelength gets absorbed rapidly by the outer surface and does not penetrate. That’s the reason Microwaves are ideal for cooking food.
How is food cooked?
The microwave bounces off the sides of the oven like a mirror but penetrates the food. Food with a lot of water content can be cooked best using a microwave. Here is why!
The microwaves specifically cause the food's water molecules to vibrate, producing heat due to friction, thereby cooking the food. And this is the same reason dry food items like bread don’t get cooked well in a microwave oven. The microwave energy is converted into heat as it is absorbed by the water, and it does not make the food radioactive or contaminated. And if you try to open the door, the magnetron stops buzzing immediately.
Additional Info for Geeks
You needn’t necessarily read the following to understand microwave ovens. But the following is interesting detailed information.
1. Electromagnetic radiation is the Electric field and Magnetic field perpendicular to each other. Let’s look at the electric field here - it oscillates (imagine pushing a pulling an object back and forth like a sinusoidal wave).
2. Here is the interesting part!! Water molecules (H20) are a dipole (the oxygen side has a partial negative charge & the hydrogen side has a partial positive charge). Hence, the electric field causes the water molecules in the food to rotate back and forth. This is why the water molecules vibrate. At a molecular level, there is friction because of this vibration. Which is causing the heat to cook the food.
Figure 2: Water molecule oscillation due to Microwaves. Red represents oxygen. White represents hydrogen.
3. The microwaves are standing waves which means, some portions of the food will not have the effect of the electric field. So the base turntable rotates to cook the food evenly and avoid hot and cold spots.
This is how Microwave ovens work!
Blog posts
I’m thinking of writing about how a Segway works for the next episode S2E5 which is coming out next week. I’ll notify you next Wednesday about the same :)
Also, by replying to this email, let me know if you’d like to read about a specific gadget/device. And I can write about it.
Gadget of the week
Smart Telescope: The eQuinox 2 is an innovative smart telescope that can be used even in brightly lit urban areas. It uses advanced image processing to filter out the effects of city lights, allowing for clear, high-resolution images of celestial objects. With this gadget, you can see the blue and red hues of the Ring Nebula or the red spot of Jupiter, even from the heart of the city. Autonomous Field Detection technology also allows it to quickly orient itself in the sky, even when only a few stars are visible.
Thank you for reading!
Have a nice rest of the week, and take care!
Until next Wednesday,
Chendur
