82510 Microscope Lab
2-1
MICROSCOPE LAB
Introduction:
The microscope is a fundamental tool for biologists. This instrument has been perfected
over the past 300 years. It has, within limits, allowed the invisible to become the visible.
The extension of the eye or vision makes much information available to the curious
student. For instance: shape, size, position, connections, colors, number, texture and even
chemical composition are some of the facts that may be recorded by the eye and the
microscope.
Types of microscopes:
Light Microscope - the models found in most schools, use compound lenses and light to
magnify objects. The lenses bend or refract the light, which makes the object
beneath them appear closer.
Scanning Electron Microscope - allow scientists to view a universe too small
to be seen with a light microscope. SEMs don’t use light waves; they use
electrons (negatively charged electrical particles) to magnify objects up to two
million times.
Transmission Electron Microscope - also uses electrons, but instead of scanning the
surface (as with SEM's) electrons are passed through very thin specimens.
You will first learn to properly use the Compound Light Microscope.
Terms:
Magnification How much larger an object appears under a scope than it actually is;
oculars are engraved with their magnifying powers; oculars magnify
10X (magnification = 10 multiplied by, for instance 4 for scanning
power = 40 times normal size).
Resolution The rendering of detail; high magnification without good resolution is
worthless; light is the limiting factor of resolution; the blue light of
your scope allows resolution of 0.2 microns.
Depth of Field The distance through which you can move the specimen and still have
it in focus; the higher the magnification, the closer the objective is to
the slide and so the depth of field decreases; this requires a more
delicate technique.
In order to see such small structures, the subject must be made larger or magnified. Thus
in microscopy, we talk a lot about magnification. However, the most important function
of your microscope is not magnification, but the rendering of detail or resolution. If a
mouse was magnified to the size of an elephant, but you could not distinguish it from an
