You probably saw a distorted image when using a magnifying glass and were
able to minimize the distorted effect by changing the distance between the mag-
nifying glass and the specimen.The Microscope
A microscope is a complex magnifying glass. In the 1600s, during the time of
Antoni van Leeuwenhoek (see Chapter 1), microscopes consisted of one lens
that was shaped so that the refracted light magnified a specimen 100 times its
natural size. Other lenses were shaped to increase the magnification to 300 times.
However, van Leeuwenhoek realized that a single-lens microscope is difficult
to focus. Once Van Leeuwenhoek brought the specimen into focus, he kept his
hands behind his back to avoid touching the microscope for fear they would
bring the microscope out of focus. It was common in the 1600s for scientists to
make a new microscope for each specimen that wanted to study rather than try
to focus the microscope.
The single-lens magnifying lens or glass is a thing of the past. Scientists today
use a microscope that has two sets of lenses (objective and ocular), which is
called a compound light microscope. Fig. 3-4 shows parts of a compound light
microscope. A compound light microscope consists of:(^54) CHAPTER 3 Observing Microorganisms
Ocular
(eyepiece)
Body
Arm
Coarse focus
adjustment knob
Fine focus
adjustment knob
Stage adjustment knobs
Interpupillary adjustment
Nosepiece
Objective lens (4)
Mechanical stage
Substage condenser
Aperture diaphragm control
Base with light source
Field diaphragm lever
Light intensity control
Fig. 3-4. Parts of a compound light microscope.