Physiology 1
Name
Redwood High School
Class Period
Using the Microscope as a Scientific Tool
Background
The human eye, for all that it can do, is a limited tool in the study of science. Many of the phenomena
which scientists must evaluate and explain occur at a size that the unaided human eye is incapable of
observing. The development of the first microscopes, in the 1600's, was an important event in the history
of scientific study. Those first microscopes were capable of magnifying an image by 40X. Since that time
microscopes and microscopy have been continually improved, so that today there are microscopes
available (not at Redwood, however) which are capable of more than 100,000X magnification. In addition
to increases in magnification, modern microscopy has developed new methods of light transmission and
new methods of staining specimens. Modern microscopes are quite often connected to cameras and
video recorders to help scientists in making careful observations.
We will use the microscopes as a tool in a number of investigations. In order to make the most of this
tool, it is necessary to become familiar with it and skilled in its use. This lab will introduce you to the
microscopes available to you and provide some basic practice in the skills of microscopy. We will also
take a quick look at some of the microscopes and microscopy techniques that are not available at
Redwood, but are very important in the larger scientific world.
Procedure/Techniques
I. Microscope Review
1. The type of microscope you will be using is pictured below. It is a compound microscope. There are
two sets of optical components: the eyepiece (sometimes called the ocular) and the objectives. The
three objectives have the following magnification ratings: 4X, 10X, and 40X. The eyepiece has a
magnification rating of 10X. The total magnification viewed at any given time is a product of the
eyepiece magnification times the objective magnification.
2. Whenever you carry the microscope you must
have one hand under the base, and another hand
on the arm.
3. Always store the microscope with the 4X
objective locked in place. Likewise, always begin
any viewing session with the 4X objective in
place.
4. If necessary, any of the lenses on the microscope
may be cleaned using lens paper only.
5. Focusing:
a.) Beginning with the 4X objective, use the
course focus knob to bring the object into focus.
Center the object in the field of view (the entire
area visible at any given magnification).
Continue to focus by using the fine focus knob.
b.) If you need to view at a higher magnification, rotate the 10X objective into place. You should only
need to use the fine focus knob from this time on. If further magnification is needed, rotate the 40x
objective into place and again use the fine focus knob.
II. Microscopic Drawing.
The following rules should be followed for all drawings using the microscope.
• Use a sharp-pointed pencil only, not ink or colored pencil.
• Drawings are to be "hard-line", not sketches, and should be as accurate and detailed as possible –
neatness counts.
• Draw only what you see, not what you think you should see.
• The drawing should be accurately to scale – that is, it should have the same proportions in your
drawing that it does under the microscope. You may enlarge the drawing relative to the field of
view, but only if you maintain scale and proportion.
• Label lines are done darkly, using a ruler. Do not cross label lines.
• Labels are lined up, neatly, along the line drawn on the right side.
Specimen
Labels:
Name
Date
Period
Illustration
size
Actual
size
Comparison
size
Title of Drawing:
Total Magnification:
Specimen
Drawing:
III. Microscopic Measurement
1. The magnification of the class microscopes is as follows:
Magnification Level
Eyepiece
Objective
low power
medium power
high power
10x
10x
10x
4x
10x
40x
Total
Magnification
40x
100x
400x
2. The field of view for each of the powers can be measured. The field of view means the diameter of
the circle that you see when viewing through the ocular (eye piece) objective. The fields of view for
the class microscopes is as follows:
Microscope Type
Swift
Magnification Level
40x
100x
400x
Field of View (µm/mm)
4300 µm/4.3 mm
1800 µm/1.8 mm
430 µm/ 0.43 mm
3. The Swift microscopes have an indexed pointer in the eyepiece. This tool permits careful and
accurate microscopic measurements. The calibrations on this ‘ruler’ indicate different measurements
under different magnifications. These measurements are summarized as follows:
Measurement
Pointmaster Distance Between
largest lines
medium lines
shortest lines
Pointmaster Lengths
arrow tip only
arrow shaft only
total arrow length
40X
100X
400X
645 µm
125 µm
25 µm
250 µm
50 µm
10 µm
62.5 µm
12.5 µm
2.5 µm
250 µm
1750 µm
1900 µm
100 µm
700 µm
800 µm
25 µm
175 µm
190 µm
4. Each drawing should contain the following measurement information: illustration size, actual size
and comparison size. Each of these should be conducted as follows:
• Illustration size is, simply, the measure of your drawing as indicated by the bracket on your
drawing. This should be expressed in millimeters (mm).
• Actual size is the size of the object indicated by the brackets on your drawing. It should be
determined by the measurement scale in the eyepiece of your microscope. It could also be
accurately estimated by comparing the size of the object to the known size of the field of
view. This measure can be expressed as millimeters (mm) or micrometers (µm).
• Comparison size expresses the relationship between the size of your drawing and the size of
the image as viewed in the microscope. It is determined by dividing illustration size by actual
size (illustration size/actual size). This comparison has no units.