The microscope is one of the most
significant tool of science. . It literally opened up worlds of organisms and
information to scientists. It is perhaps the most important tool for you to
understand as a biology student. You should be able to:
Tools of Biology
The Microscope
The microscope is one of the most
significant tool of science. . It literally opened up worlds of organisms and
information to scientists. It is perhaps the most important tool for you to
understand as a biology student. You should be able to:
**name all of its parts and describe the function of each
**explain how to carry the thing, properly prepare a slide, & focus correctly
**calculate total magnification
**estimate the size of a specimen being observed
Let's Get Started!!!
Introduction
"Micro" refers to tiny, "scope" refers to view or look at. Microscopes are tools used to enlarge images of small objects so as they can be studied. Microscopes range from a simple magnifying glass to the expensive electron microscope. The compound light microscope is the most common instrument used in education today. It is an instrument containing two lenses, which magnifies, and a variety of knobs to resolve (focus) the picture. It is a rather simple piece of equipment to understand and use.
1. eyepiece-where you look through to see the image of your specimen.
2. body tube-the long tube that holds the eyepiece and connects it to the objectives.
3. nosepiece-the rotating part of the microscope at the bottom of the body tube; it holds the objectives.
4. objective lenses-(low, medium, high, oil immersion) the microscope may have 2, 3 or more objectives attached to the nosepiece; they vary in length (the shortest is the lowest power or magnification; the longest is the highest power or magnification).
5. arm-part of the microscope that you carry the microscope with.
6. coarse adjustment knob-large, round knob on the side of the microscope used for focusing the specimen; it may move either the stage or the upper part of the microscope.
7. fine adjustment knob-small, round knob on the side
of the microscope used to fine-tune the focus of your specimen after using the coarse
adjustment knob.
8. stage-large, flat area under the objectives; it has a hole in it (see aperture)
that allows light through; the specimen/slide is placed on the stage for viewing.
9. stage clips-shiny, clips on top of the stage which hold the slide in place.
10. aperture-the hole in the stage that allows light through for better viewing of the specimen.
11. diaphraghm-controls the amount of light going through the aperture.
12. light or mirror-source of light usually found near the base of the microscope; the light source makes the specimen easier to see.
1. Always carry the microscope with two hands - one on the arm and one underneath the base of the microscope. Hold it up so that it does not hit tables or chairs. Never swing the microscope.
2. Do not touch the lenses. If they are dirty, ask your teacher for special lens paper or ask the teacher to clean the lenses for you. Teachers - remember that you may use a soft cloth dipped in a small amount of isopropyl alcohol to clean the lenses.
3. If using a microscope with a mirror, do not use direct sunlight as the light source. Eye damage can result. If using a microscope with a light, turn off light when not in use.
4. Be cautious when handling glass slides and coverslips. Notify teacher if a slide or coverslip breaks. Students should not handle broken glass.
5. Always clean slides and microscope when finished. Store microscope set on the lowest objective with the nosepiece turned down to its lowest position (using the coarse adjustment knob). Turn off light.
6. Cover microscope with dust cover and return microscope to storage, if requested by teacher.
Frequently Asked Questions
1. Why is called a "compound" light microscope ?
"Compound" just refers to the fact that there a two
lenses magnifying the specimen at the same time, the ocular & one of the objective
lenses.
2. If two lenses are always magnifying the
specimen
(see #1), how do you figure out the total magnification being used ?
You multiply the power of the ocular and the power of the
objective being used. total mag. =
ocular x objectiveFor example, if the ocular is 10x and the low power objective is 20x,
then the total magnification under low power is 10 x 20 = 200x.
3. How do you carry one of those things ?
With two hands, one holding the arm & the other under the
base.
4. What about focussing ? How do you do that ?
Here's what I suggest. Once you have your slide in place
on the stage, make sure the low power objective (the shortest objective lens) is in
position & turn the coarse focus until the lens is at a position closest
to the stage. Set the diaphragm to its largest opening (where it allows the most
light through). Then, while looking through the ocular, begin to slowly turn the
coarse focus. Turn slowly & watch carefully. When the specimen is
focussed under low power, move the slide so that what you want to see is dead-center
in your field of view, & then switch to a higher power objective. DO NOT touch
the coarse focus again --- you will break something ! Once you are using a high
power objective, focus using the fine focus knob ONLY. Be sure to center your
specimen before switching to a higher power objective or it may disappear.