Hey, how do microwave ovens work? And more importantly, how do the microwaves
stay in the microwave? The simple explanation is that microwaves
are actually too big to get out of the oven. But we can do better than that.
So let's dig a little deeper into this hot pocket of science.
Microwave radiation has several key properties that make it useful for cooking.
First, it's not too risky to use at home because it's a form of low-frequency,
non-ionizing radiation. Like radio waves, infrared, and visible light.
This is opposed to dangerous, high-energy, ionizing radiation like X-rays and gamma rays
that have a relatively high chance of damaging DNA and causing cancer
and a small chance of transforming you into a giant green rage monster.
That's not to say that microwaves can't hurt you. After all, humans are much like hamburgers
in the sense that we are both made of flesh. At high enough levels, microwaves can cause burns
and other physical damage, which is why it's important to keep them contained.
Second, microwaves interact with polar molecules,
which are made of both positively and negatively charged atoms,
causing them to spin. The extra energy from the spinning
then radiates from the molecules as heat. In the case of food, these are typically water molecules
where the oxygen atom has a positive charge while the two hydrogen atoms have a negative charge.
But microwaves don't interact much with other kinds of molecules.
They really just bounce off them, meaning that microwaves can be easily contained
by, say, a small closed metal box.
That's how microwaves heat just the food and not the surrounding air or the sides of the oven.
This is also why it's not a good idea to run a microwave oven while it's empty.
Without the water molecules in food to absorb the microwaves,
they can end up damaging the device's electronics over time.
As for putting metal in the microwave, well, it won't make the device explode,
but pointed metal objects might spark due to electric charge building up at the tips,
which, incidentally, is also why Guy Fieri's hair always looked like that.
But hey, what about that window? Electromagnetic radiation like radio waves
and microwaves can pass through glass, right? The reason why microwave ovens don't melt your face off
when you look in the window is because they're essentially a kind of Faraday cage
that blocks electromagnetic waves above a certain size
from getting in or out. You've probably noticed that the window
of a microwave door has a fine mesh embedded in it. Those holes are more than big enough
for visible light to escape, like a mouse darting out of an elephant pen,
but they're way too small for the microwaves to get through. Microwaves are quite a bit bigger than waves
in the visible light spectrum, which are only around 400 to 700 nanometers long.
The microwave spectrum is from a millimeter to 30 centimeters, or about 12 inches.
Microwave ovens use a frequency around 2.45 gigahertz,
which results in waves around 4.8 inches in size,
which is way bigger than these holes. These are simply not microwave-shaped holes.
A microwave oven is typically only unsafe if the door no longer seals,
the device has a hole in it, or it has been modified to run with the door open
as an ammo-saving way to defend your compound in a zombie apocalypse.
It's also an unsafe place to store elements like radium
that emit gamma radiation, because gamma waves are small enough
to get through the holes in the door's mesh. I'm hoping that none of you are currently
storing radium in the microwave, but if you are, please stop. And don't worry about opening the door
immediately after cooking. Microwaves travel extremely quickly,
so they'll be absorbed into the food long before the door opens.
Although waiting for a little bit does have the advantage of allowing any hot spots
to dissipate more evenly throughout the food. But that's up to you,
and how much of an appetite you still have after I made you think about cooked zombies just now.
I'm sorry. That was a Techquickie, and it's over now. Thanks for watching.
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