First of all, since the microscope is very expensive, lets try to figure
out a few ways to AVOID the school having to bill YOU for the cost of replacing
one!
How to figure out the magnification: eyepiece x objective
lense = magnification
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Eyepiece Magnification |
Objective Lense Magnification |
Microscope Magnification |
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Scanning Objective |
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Low Power |
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High Power |
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Procedure:
1. Make sure all backpacks are out
of the aisles before you get a microscope! Always carry the microscope with one
hand on the arm and one hand on the base. Carry it close to your body.
Always take the microscope with the number you signed up for. You are
responsible for this microscope!
2. Remove the cover, plug the
microscope in, and place the excess cord on the table! If you let the excess
cord dangle over the edge, your knee could get caught on it, and the next sound
you hear will be a very expensive crash.
3. Make sure the microscope is OK.
If not, tell your teacher! Otherwise you will be made responsible for any
damage or missing parts!
4. Always start and end with the Scanning Objective (the smallest objective)!!!
5. Open the diaphragm.
6. Lower the microscope stage to the lowest point. Place the slide on the stage with the specimen directly over the center of
the glass circle (or hole) on the stage (directly over the light). Then you
have a 9 out of 10 chance of finding the specimen as soon as you look through
the eyepiece!
NOTE: If you wear glasses, take them
off; if you see only your eyelashes, move closer. Look through the eyepiece with one eye and try to keep
the other eye open (this helps avoid eye strain). Remember, everything is
upside down and backwards!
7. Make sure you are on the SCANNING
OBJECTIVE, lower the objective lens to the lowest point, then focus using first
the coarse knob, then the fine focus knob. The specimen will be
in focus when the SCANNING OBJECTIVE is close to the lowest point, that’s why
you start there and focus by slowly raising the lens. If you can’t get it at
all into focus using the coarse knob, then switch to the fine focus knob.
8. Adjust the diaphragm as you look
through the eyepiece, and you will
see that MORE detail is visible when you allow in LESS light! Too much light
will give the specimen a washed-out appearance. TRY IT OUT (also with the
higher magnifications)!
9. Once you have found the specimen
with the SCANNING OBJECTIVE, center the specimen in your field of view and fasten it with the stage clips. Then, without changing the focus knobs, switch it to
LOW POWER. If you don’t center the specimen you will lose it when you switch.
10. Be careful when focusing, use
the coarse focus knob as little as possible. If you have difficulty focusing,
look at the objective lens and the stage from the side and turn the coarse
focus knob so that the objective lens moves downward or the stage, if it moves,
goes upward. Move it as far as it will go without touching the slide, then
carefully move the lense away from the stage.
11. When you switch to HIGH POWER
only use the fine focus knob!!! Do not remove the slide when it is on HIGH
POWER. The HIGH POWER objective is very close to the slide. Use of the coarse
focus knob will scratch the lens, and crack the slide. More expensive sounds .
. .
Tips On Making Good Drawings:
1. Don’t even think of starting your
drawing unless you have a PENCIL! Drawings in PEN are UNACCEPTABLE! This is for
two reasons:
(a) You can erase pencil!
(b) You can shade in areas more easily in
pencil.
2. Each drawing must be about 1/2
page in size, and must include clear, proper labels! Draw a circle with a pair
of compasses (Zirkel). The circle indicates the field of view as seen through
the eyepiece. In the upper left hand corner of each circle include the specimen
name as written on the slide label
or the blackboard. In the upper right hand corner, include the magnification.
3. Labels should start on the
outside of the circle. All arrows should end with the point touching the object
to be labeled! An unlabeled drawing is nothing more than scratches on a piece
of paper!
How To Make A Wet Mount (Nasspräparat):
1. Gather a thin slice/piece of
whatever your specimen is. If your specimen is too thick, then the coverslip will wobble on top of the
sample like a see-saw.
2. Place ONE drop of water directly
over the specimen. If you put too much water over the specimen, then the
coverslip will float on top of the water, making it harder to draw the
specimens as they float past the field of view! If too little liquid is used,
the organisms may be crushed by the cover glass and evaporation will dry up the
specimens quickly.
3. Place the coverslip at a 45
degree angle (approximately), with one edge touching the water drop, and let
go. Coverslips are very fragile and break easily, handle with care!
How To Stain a Slide:
1. Place one drop of Methylene Blue stain (be careful, don’t
get stains on your clothes, they don’t wash out!!!) on one edge of the
coverslip, and the flat edge of a piece of paper towel on the other edge of the
coverslip. The paper towel will draw the water out from under the coverslip,
and the cohesion of the water (due to the Hydrogen Bonds) will draw the stain
under the coverslip.
2. As soon as the stain has covered
the area containing the specimen you are finished. The stain does not need to
be under the entire coverslip. If the stain does not cover the area needed, get
a new piece of paper towel and add more stain until it does.
3. Be sure to wipe off the excess
stain with a paper towel, so you don’t end up staining the objective lenses!
4. You are now ready to place the
slide on the microscope stage. Be sure to follow all the instructions on how to
use the microscope.
When you have completed your drawings:
1. Turn the revolving nosepiece so that the SCANNING OBJECTIVE objective lens
is "clicked" into position!
2. Remove the specimen from the
stage.
3. Be sure to wash and dry both the
slide and the coverslip and return them to the correct places!
4. If necessary, clean the objective
lenses (only with a special lense paper! And never ever touch the lenses with
your fingers!!!) and the stage.
5. Unplug the microscope and wrap
the electric cord.
6. Take the microscope by its arm
and base and return it to the shelf.
7. Clean your table!
NOTE: These procedures will remain the same,
regardless of the type of stain, or the addition of a hypertonic/hypotonic
solution to your specimen.
REMEMBER: Be careful with the equipment, and be
sure to leave the lab in the same condition it was in when you arrived.
HAVE FUN!
Common problems and solutions
1. Image is
too dark!
Adjust the diaphragm, make sure your light is on.
2. There's
a spot in my viewing field, even when I move the slide the spot stays in the
same place!
Your
lens is dirty. Use lens paper, and only lens paper to carefully clean the
objective and eyepiece lens. The eyepiece lens can be removed to clean the
inside.
3. I can't
see anything under high power!
Repeat the scanning and low power procedure, then switch back to high
power.
4. Only
half of my viewing field is lit, it looks like there's a half-moon in there!
You probably don't have your objective fully clicked into place.
http://shs.westport.k12.ct.us/mjvl/biology/microscope/microscope.htm
http://www.microscope-microscope.org/basic/how-to-use-a-microscope.htm