345
Microscopes
electron microscopes
objects must be cut into thin
slices in order to see them with
a microscope. However, a
scanning electron microscope
can magnify a whole object
such as this ant (right), which
is about 15 times
normal size.imaging atoms
special electron microscopes can show individual
atoms, which are so small that a line of 0.5 million
atoms would only span the width of a human hair.
this piece of silicon (above) is magnified
45 million times, revealing its atoms.With a
scanning
electron
microscope the
image appears
on a monitor.Optical microscopes can reveal
living cells such as these cells
that come from a human cheek.
They are magnified more than
200 times.although the romans used magnifying
lenses about 2,000 years ago, the first
true microscope appeared around
1590, built by Dutch lensmakers
Hans and Zacharias Janssen. in 1663,
english scientist robert Hooke studied
insects and plants with a microscope.
He found that cork was made up of tiny
cells, a discovery of great scientific
importance. microscopes aroused great
interest in microscopic life, as this old
etching shows.InventIng the mIcroscope
optical microscope
the optical, or light, microscope has two
main lenses: the objective and the eyepiece.
High-quality microscopes contain several
additional lenses that help to give a clear, bright
image. Different objectives can be fitted that give
a range of magnification from about 10 times
to 1,500 times normal size.WitHin all obJects there is a hidden world that is much
too tiny for us to see. With the invention of the microscope
in the 16th century, scientists were able to peer into this
world and unravel some of the great mysteries of science.
they discovered that animals and plants are made of
millions of tiny cells, and later were able to identify the
minute organisms called bacteria that cause diseases.
early microscopes consisted of a single magnifying lens;
today’s microscopes have several lenses and can be used
to see very tiny objects. electron microscopes are even
more powerful. instead of light, they use a beam of
electrons—tiny particles that are normally part of
atoms—to magnify objects many millions of times.
scientists use electron microscopes
to study the smallest of living
cells and to delve into the
structure of materials such
as plastics and metals.Find out more
atoms and molecules
biology
microscopic lifeA strong beam
of light strikes a
mirror under the
microscope.
The beam shines
onto the object
from below.Condenser lenses
concentrate a
beam of light
onto the object.The object being
studied rests on
a glass slide.The objective
lens produces an
image which the
eyepiece magnifies
(makes larger).Objective lenses of
different power can be
swung into position
when needed.Observer looks
through eyepiece.US_345_Microscopes.indd 345 22/01/16 11:11 am