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BISC 101 Chapter Notes -Zoom Lens, Microscope Slide, Optical Microscope

Biological Sciences
Course Code
BISC 101
Derek Bingham

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Cell Structure Lab Prep 1
Major parts of a compound microscope and their functions
Specimen drawing
Identify major parts of a compound microscope and their functions.
Demonstrate the steps involved to focus on a specimen.
Draw and label the specimens.
Calculate total magnification, specimen size, and drawing magnification.
The Compound Microscope:
The eye pieces multiply by 10x already so…
Objective Lens
Total Magnification

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Cell Structure Lab Prep 2
Bringing a Specimen into Focus with the Compound Microscope:
It is likely that the only controls you will have to adjust are:
Light intensity
Course focus
Fine focus
Mechanical stage
Iris diaphragm
1. Obtain a slide.
2. Switch on the light source.
3. Swing 4x objective into
4. Place your slide, coverslip up, on the stage and clip it into place with the spring-mounted arm on the
mechanical stage.
5. Raise the stage to its highest position using the course focus. DON’T FORCE IT PAST THE HIGHEST POINT!
6. Using the mechanical stage controls, adjust the slide until the portion of the slide you wish to examine is
directly under the objective and is illuminated in the light path.
7. Adjust the distance between the eyepieces to suit your eyes
8. Look through the eyepieces and adjust the light intensity so that it is comfortable to your eyes.
9. Using the coarse focus knob, slowly lower the stage until the image of the specimen is clear and sharply in
10. Using the mechanical stage control knobs, move the slide around until what you are interested in viewing
is in the centre of the field of view.
11. Coarse focus is ONLY used with the 4th objective in place. To now view the specimen at 100x
magnification, carefully swing the 10x objective into place, while watching from the front of the
microscope. You don’t need to lower the stage when changing objectives the lens won’t hit the slide.
The objective lens will click into place when it is in the correct position.
12. Focus using the fine focus knob only.
13. To view the specimen at 400x magnification, carefully swing the 40x objective into place, while watching
from the front of the microscope. You don’t need to adjust the stage when changing objectives the lens
will be very close but won’t hit the stage. It WILL be very close though.
14. Focus using the fine focus knob only.
15. When viewing an object, you may find it useful to adjust the contrast of the image to make structures
more readily seen. This is done by moving the iris diaphragm control either to the left or right.
16. When you are finished examining your specimen:
a. Put the 4x objective back into place before removing the slide.
b. Do NOT move the stage up or down.
c. Turn off the light.
d. Replace the dust cover.

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Cell Structure Lab Prep 3
1. All drawings should be done on clean, white unlined drawing paper or in the manual if space is provided.
Don’t put more than two diagrams on one page.
2. All drawings should be 2D line drawings using a sharp drawing pencil. NO PENS! Don’t draw fuzz/sketchy
lines. Do not color or shade in your drawing.
3. All drawings should be labeled with a thin line drawn with a ruler running from the label to the part of the
drawings being identified. Don’t put arrowheads on the lines. Labels should be printed outside the
drawing. Do not cross label lines. Draw the shortest possible start line from the object to the label.
4. Each drawing should have an underlined title using uppercase letters, and should always include the
microscope magnification from which the drawing was made.
5. If requested, the drawing must include: the calculation for actual size, a scale bar placed outside of the
drawing, and a record of the drawing magnification. Instructions for calculations are below.
Calculation of Total Microscope Magnification:
Total magnification is calculated by multiplying the power of the objective lens being used by the power of the
eyepiece. Record total microscope magnification on all drawings!
10x eyepiece times a 40x objective = 10x40 = 400x.
Calculation of Width of Field of View:
Field of view lighted circular area you can see when looking into the microscope
Magnification of an object within this circle depends upon the power of the objective you are looking through (as
you “zoom in” with the higher objectives, the magnification increases while the diameter decreases). You need to
know the value of the diameter in order to estimate the size of whatever object you are viewing. Instructions for
measuring field of view for 4x, 10x, 40x follow.
Complete Table 2 below by performing these steps:
1. Determine the diameter of FoV for the 4x objective by placing a plastic ruler on the stage so that you can
see the millimeter divisions when you look through the eyepieces. Be sure to place a ruler line at the very
edge of your FoV, which will count as your “zero.” Count the number of 1mm graduations of the rule that
span the FoV across the diameter (widest part of circle). Record the # of 1mm graduations in Table 2.
2. Remember that increasing the magnification on a microscope is like using a zoom lens on a camera. As
you increase magnification, the object that you view appears larger but the area that you see through the
lens is actually less.
3. The FoV diameters for the 10x and 40x objectives are approximately proportional to their relative
magnifications. The 10x objective lens magnifies things 2.5x more than the 4x lens. Therefore, the
diameter of the FoV using the 4x objective is approximately 2.5 times more than the diameter of the FoV
using the 10x objective. To calculate the FoV on the 10x objective, divide your measurement for the 4x
objective by 2.5. Put your answer in the appropriate box in Table 2.
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