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microscopy
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MICROSCOPY
Compare and contrast light and electron microscope
Discovered by Romans in the first century AD microscope is one of
if not the most important scientific equipment. Since then
microscopes have been altered as technology grew so they can
give us a clearer picture of the specimen. Today there are two
types of microscopes light and electron microscope. Light
microscope is a type of microscope, which uses light and magnifying
glass to inspect things that are
too small to be seen by the naked
eye, or finer detail than the
necked eye is able to pick up.
Electron microscope is a type
microscope, which fires a highly
energetic electron to study
things that are too small to be
seen by light microscope such as
viruses.
Light microscopes have a
resolution of 200nm, if two object are closer than 200nm they appear as one object
therefore, there is no chance of being able to look at the internal structure of a cell.
This is because light microscopes use light to magnify object if light cannot pass
through the two objects they are not distinguished as separate objects. Electron
microscopes however have a resolution of 0.1nm as electrons are smaller than light
waves and therefore can pick up much more detail than light microscope.
Since electron microscopy uses charged electrons they cannot be fired at anything
and they must be used in a vacuum chamber therefore when preparing the specimen
all moisture must be removed or the water in the specimen will boil and destroying it.
Light microscopes are small and relatively cheap
therefore can be purchased and used for education
purposes electron microscopes however are expensive
and can only be used for medical purposes. Specimen for
light microscope are stained to make it more visible and
to allow contrast between different parts of the cell.
Electron microscope work differently than light microscope, as electrons cannot be
seen the image is projected on to a screen. Unlike light microscopes, the image is
shown in black, white and shades of grey. The colour is then added on special
computer software.
There are two types of electron microscopes
Transmission electron microscope (TEM) and Scanning
electron microscope (SEM). Transmission electron
microscope passes through a thin prepared sample. It
passes through a denser part of the cell less easily giving
some contrast. This type of electron microscope has a
magnification of X5000. However, the electrons damage
thin tissue therefore must be coated with thin layer of
heavy metal such as gold. In Scanning electron
microscope is beamed onto a specimen however, the
electrons do not pass through rather bounce off the sampler creating a 3D image.
However, the magnification is only X1000 so does not pick up as much detail as TEM.
Scanning electron microscope can provide the detail of the external structure rather
like what is formed by the eye whereas Transmission electron microscope probes the
internal structure of solid and gives us the microstructure of cells not seen by the
necked eye. Therefore, we can learn more about what we are made of more
efficiently.
Although both types of microscope are indeed, very helpful nether one is without the
limitation. However they allowed as to explore and see in detail the cell structure of
living organisms developing our ideas of life and its constituency.
BETLEHEM SIRAK FEKADE
BIOLOGY
MR BONNING