14th century, Italian monks developed the art
of grinding lenses; these lenses were made into spectacles to
improve the monks' failing eyesight
In 1590, Hans and Zacharias Janssen (Dutch lens
grinders) mounted 2 lenses in a tube to produce the first compound
microscope (one with 2 main lenses).
In 1665, Robert Hooke used a crude compound microscope
to observe thin slices of cork cells from 'cork oak' trees. Cork
is the very fast growing bark of the tree. The bark can be periodically
stripped from a tree and used to build ships as it is a very durable
wood that resists rotting from water and mold when wood is constantly
wet. Hooke may have studied cork because it was economically very
valuable to the English and their ship-building industry.
Around the same time as Hooke, Anton van Leeuwenhoek
used a simple microscope (1 lens) to look at blood, rainwater,
teeth scrapings, etc.
A Light microscope - is a compound microscope
that uses mirrors or a light source to better view a specimen.
Transmission electron microscope was invented
in the 1930's. It forms an image by electrons passing through
a specimen. It is capable of higher resolution than the scanning
Scanning electron microscope was developed later
than transmission electron microscope. It forms an image by having
electrons bombard the surface of the specimen and allowing the
secondary (lower energy) electrons to be emitted.
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06, 1998 by: Glen
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