THE MICROWAVE, EXPLORED
UNDERESTIMATED COUNTERTOP CONTRAPTIONS
Microwave radiation
wavelength 12.8cm
That bag of popcorn is just the beginning. First sold in 1947, the
microwave oven wasn’t a common household item until the late 1960’s.
Along with the fridge, conventional oven, blender, and coffeemaker, it
is now considered an essential appliance in the American kitchen. But
while we all use it to warm up coffee and pop our corn, this countertop
contraption remains poorly understood and often underestimated.
Microwaves don’t cook food from the inside out—a common myth—and
despite the term “nuke,” it’s not nuclear radiation that’s reheating your
frozen burrito. What’s more, microwaves can outperform traditional
cooking techniques when it comes to vegetables, fried snacks, and
quick soups. Put aside the Pop Secret—it's time to take a deeper look
at the humble microwave.
ANATOMY OF A MICROWAVE OVEN
HOT POCKET
For the microwave’s invention, thank
Percy Spencer’s sweet tooth. The
Raytheon engineer was lingering in front
of an active microwave radar set when
the Mr. Goodbar in his pocket began to
melt. Ingredients used in Spencer’s early
food-heating experiments include
popcorn kernels and an egg (which
exploded in a colleague’s face).
1 The power source converts 110–220 volts to the
much-higher voltage needed to generate microwaves.
2 A magnetron is special type of vacuum tube that uses
a flow of electrons to stimulate microwave radiation through
resonance.
3 A wave guide directs microwaves from the magnetron
to the food.
4
5
3
4 A fan makes the microwaves uneven, counterintuitively
causing the heat to be more even.
2
5 The oven chamber is sized proportionally to the
wavelength of microwaves so that standing waves can form.
6
7
KNOW YOUR NODES
1
6 The turntable is a spinning plate that revolves food around
inside the oven so that it moves through hot and cold spots in
the standing wave.
7 The window features a layer of conductive mesh with
small holes sized so that light can travel through them, but
the much-larger microwaves cannot.
TURN ON THE WATER
Microwaves are a particular wavelength
of electromagnetic radiation, just like
light waves are. But microwaves are
capable of causing polarized water
molecules to attempt to flip back and
forth billions of times a second. The
water molecules can’t do it fast enough,
and the ensuing collisions raise the
temperature of the food.
Maximum amplitude: hot spot
Node: still cold
Remove your microwave’s turntable, place a slice
of pizza inside, and heat for 15 seconds. You’ll
notice some parts of the cheese will melt and
some will not. Here’s what’s happening: Energy
is greatest at the standing wave’s peaks and
valleys—called anti-nodes—and there’s zero
energy at the nodes, where it crosses the x-axis.
The nodes correspond to cold spots in the oven,
where no heating takes places. The turntable
keeps food moving through these hot and cold
spots so that it heats more evenly.
Nerd fun: Measure the distance between melted
areas on your pizza, then double it to get the
wavelength. Multiply that number by the
machine’s frequency (2,450MHz) and multiply
that by the wavelength. You should come up with
the speed of light (299,792,458 meters / 186,282
miles).
H2O orients to oscillating waves
-
+
Like this, but 2.45 billion times per second
FOOD AS ANTENNAE
Like an antenna that is too small,
a single popcorn kernel doesn’t receive
the waves.
As a mass, the kernels receive the
signal loud and clear. POP!
In conventional ovens, small foods cook faster than larger ones. It tends to be the
opposite with microwaves. Think about microwaving popcorn: In about 60 seconds,
almost all the kernels pop. But the remaining kernels puff up way more slowly.
Grouped together, all the kernels form a target mass that can “see” the microwaves
and absorb them, similar to how a radio antenna picks up radio waves. The rogue
kernels create a much less effective antenna, thereby taking longer to pop.
ChefSteps
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to become a better cook—with or
without the power of microwave
technology.