The
Accidental
Discovery of the
Microwave
意外的發現
–
微波爐
By Jason Long Him Cheung
張朗謙
This article may be
useful as supplementary
reading for physics
classes, based on the
DSE syllabus.
根據物理科文憑試課程
綱要，本文或可作為
有用的補充讀物。
Many
m o d e r n
inventions, such as the airplane
o r t h e c o m p u t e r , w e r e
painstakingly honed and refined
to work as intended. Others
were encountered upon by mere
happenstance. Arguably one
of the most ubiquitous kitchen
app l i ances , the mi crowave
oven, was invented by accident
during World War II – a period
that pres su red the creat i ve
geniuses of the world to match
the demands of weapon r y,
esp i onage techno l ogy and
vehicles. Some of these were
inadver tently translated into
practical equipment that made
t he i r way i nto ma i n s t r eam
consumerism.
Most of us are familiar with
the microwave oven. Convenient
to heat up food in a matter of
minutes and safe to use, the
microwave is both a staple of
every kitchen and a revolution
to food p repa rat i on i n t he
dining industry. Life without the
microwave is hard to imagine. But
it wasn’t until 1946 when the first
microwave was sold, and 1967
when it was initially introduced
into consumer markets for home
use.
The man of the hour was
Percy Spencer. A leading expert
in radar technology in Wor ld
War II, he was responsible for
deve l op i ng comba t r ada r
equipment that detected and
tracked increasingly dangerous
enemy aircrafts for hundreds
of miles, even when cloaked
i n da r k nes s . A t ube k nown
as a magnetron was used to
gene rate sho r t wave l ength
microwaves. It involved a high-
powered vacuum that imposed
an interaction between a stream
of electrons and a magnetic
field.
At the time, Spencer worked
on the maintenance of shor t
wave l eng t h rada r s i n co l d
weather. He just so happened
to reach into his pocket for a
candy bar, and noticed that
it had melted even in the cold
temperatures, concluding that
microwaves were responsible
for the heat generated. He then
proceeded to heat up popcorn
and an egg, the latter of which
exploded under the unreleased
pressure. Spencer found that
by trapping microwaves in a
metal box, temperatures in the
box increased significantly and
heated up food.
Microwaves are made of
an ensemble of relatively short
electromagnetic wavelengths
ranging from 1 m to 1 mm, and
have frequencies of 300 MHz to
300 GHz. The microwave oven
(not to be confused with the
electromagnetic microwave),
makes use of the f requency
of 2.45 GHz. Working primarily
on dipole water molecules in
food, the electromagnetic field
forces the water molecules to
rea l ign themse l ves wi th the
changing polarity. The friction of
