The Microscope - How Does That Work

How Does That Work?
The Microscope: A Bit of History
Microscopes give us a large image of a tiny object. The microscopes we use in school and at home trace their
history back almost 400 years.
The first useful microscope was developed in the Netherlands between 1!0 and 1"0#. There is almost as
much confusion about the inventor as about the dates. Three different eyeglass makers have been given credit
for the invention. The possible inventors are $ans %ippershey &who also developed the first real telescope'(
$ans )anssen( and his son( *acharias.
%ens +uality in early microscopes was often poor so the images were not very clear. ,ut even these rather
crude microscopes were a great help in learning more about animals and plants.
How It Works
The microscope works a lot like a refracting telescope e-cept that the object is very close to the objective lens.
%et.s put a tiny organism &a /daphnia/ or water flea' we found in pond water on a glass slide. The clips on the
microscope.s flat stage hold the slide in place. Now take a look through the microscope eyepiece. 0 mirror at
the bottom of the microscope reflects light rays up to the daphnia through a hole in the stage. 1bjective lenses
magnify the image which is made even larger when we see it through the eyepiece lenses.
The number marked on the objective lens tells us how many times the organism we have on the slide is
being magnified. 2t says 40-. 3ow( that means the tiny daphnia is forty times larger than life. To focus we can
move the objective lens closer to or farther from the organism.
The objective lens is usually a compound lens( a combination of two lenses made from different kinds of
glass. 3hen only one lens is used( we often get distortion. This distortion &chromatic aberration' is caused
because the colours making up light are not refracted &bent' the same amount when passing through a glass
lens. 3hen we use a compound lens( any distortion from the first lens is corrected by the second lens.
Microscope Facts
2n the 1""0s( a ,ritish physisist and inventor named 4obert $ooke used a microscope to study a thin piece of
cork. $e called the small( hollow sections he saw /cells/ &as in tiny rooms'. $ooke was actually looking at cell
walls( but the name stuck.
5lectron microscopes use beams of electrons instead of light. The electron beam is moved around using
magnets which act like the lenses in an ordinary microscope. 5lectron microscopes can magnify objects over
600(000 times.
7sing a scanning tunneling microscope &8TM'( scientists have actually been able to look at atoms( minute
units of matter. The computeri9ed 8TM moves above a material. 5lectrons jump from the tip of the 8TM to the
surface of the material being scanned. This creates an electric charge. The electric current changes as the tip is
moved across the material. ,y moving the tip back and forth across the material( the computer can map the
electron clouds &and the atoms'.
Food For Thought
:ifferent types of microscopes have been used to look at human cells( identify minerals( solve crimes( see how
free9ing affects food( study metals( and find the causes of crop diseases. Microscopes are an essential tool in
medicine too. They have been used to identify the causes of many deadly diseases like malaria and
tuberculosis. Microscopes can also help to find out why a person or animal died.
8cientists can even use a microscope to figure out where illegal drugs come from. ;or e-ample( looking at
opium crystals through a microscope reveals different shapes depending on where the poppies they came from
were grown. This information can help pinpoint the source of illegal drugs.
<ou can do all kinds of ama9ing things at home with a microscope. Try looking at plants( paper( cloth(
sugar( pond water( even the odd flea. %ots of a+uarium supply stores sell tiny shrimp( called brine shrimp(
which are really interesting to look at through a microscope. The possibilities for what you can find out with a
microscope are endless. 0nd who knows you might identify something new and it may even get named after
you=
For Further Information
Looking at Microscopes by >eter :. 4iley &1!#'. 8hort( basic introduction to different types of microscopes
and their uses.
Experimenting With a Microscope by Maurice ,leifeld &1!##'. ,eginner.s guide to using a microscope
including looking at plants( animals( and everyday objects.
The Complete Beginner's Guide to Microscopes and Telescopes by 0aron 5. ?lein &1!#0'. This book
offers some tips about what to look for when buying a microscope( hints about using your microscope( and
some of the things you can e-amine under a microscope &organisms that live in pond water( your own cells(
pollen( plants( cloth( yeast'.
Microscopes and Magnifying Lenses by )anice @anAleave &1!!B'. 8ubtitled /MindCboggling Ahemistry
and ,iology 5-periments <ou Aan Turn 2nto 8cience ;air >rojects/( this book covers 60 topics that you can
e-plore even if you don.t have a microscope.