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Topic:Microscopes
Keyword:HX4122
Types of Microscopes
Different types of microscopes have different qualities and uses.
Microscopes vary in magnification and resolution capabilities,
which affect the overall quality of the images they produce.
Microscopes also have different limitations. For example, electron
microscopes have high magnifying power, but they cannot be used
to view living cells. Light microscopes have lower magnifying
power, but they can be used to view living cells.
Compound Light Microscope
Light microscopes that use two lenses are called compound light
microscopes. In a typical compound light microscope, such as the
one shown in Figure 3,a light bulb in the base shines light up through
the specimen, which is mounted on a glass slide. The objective lens,
closest to the specimen, collects the light, which then travels to the
ocular (AHK yoo luhr) lens, closest to the viewer’s eye. Both lenses
magnify the image. Thus, a microscope with a 40objective lens and
a 10ocular lens produces a total magnification of 400.
Why not add a third lens and magnify even more? This approach
does not work because you cannot distinguish between two objects,
or “resolve” them, when they are closer together than a few hun-
dred nm. When the objects are this close, the light beams from the
two objects start to overlap!
52 CHAPTER 3Cell Structure
Ocular lens Magnification: 1,500
Specimen
Stage
Focus
knob
Light source
Objective
lens
In a compound light microscope, a specimen is mounted on a glass slide and
is illuminated with a beam of light from below.
Figure 3 Compound light microscope
LM of sperm
