Microscope
Lab - Using the Microscope and Slide Preparation
1. Magnification
The magnification written on the ocular lens (eyepiece) is _____________
The magnification on the Scanning objective _______Low Power Objective __________High Power Objective _________
What is the total magnification for each lens? (multiply scanning x the objective)
Scanning
________________ Low Power ____________________ High Power _____________________
2. Diaphragm
Examine
the diaphragm, what are the numbers written on it? ____________________
Which setting makes the specimen appear the brightest? __________________ darkest? ____________________
3. Lenses
Twist the ocular lens, does yours have a pointer? _____________ What is the purpose of the pointer? __________________________________
Find out what happens to your viewing field if you do not have an objective fully clicked. Describe _________________________________________
4. Viewing a Slide
Obtain a prepared E slide. Focus the slide first with the scanning objective, then click to lower power and focus again. Finally, focus the slide under high power. Remember, at high power, you should ONLY use the fine adjustment knob.
Draw the E exactly as it appears in your viewing field for each magnification. The circles below represent your viewing field. The E should take up as much space in the drawing as it does in your viewing field while you're looking at it.
| Scanning
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Low Power
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High Power
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5. Depth Perception
Obtain a prepared thread slide. You will only need to view it under scanning at this point. Your task is to figure out which thread is on top, which is in the middle, and which is on bottom. You should notice that as you focus the thread, different thread will come into focus at different times. The one that comes into focus the first should be the top thread.
What is the color order of your threads? __________________________________________________________
6. Making a Wet Mount of a Slide
1. Gather a few strands of cotton from a cotton ball using forceps. If your specimen is too thick, then the coverslip will wobble on top of the sample like a see-saw, and you will not be able to view it under High Power.
2. Place ONE drop of water directly over the specimen. If you put too much water, then the coverslip will float on top of the water, making it hard to draw the specimen, because they might actually float away. (Too much water can also make a mess.)
3. Place the coverslip at a 45 degree angle (approximately) with one edge touching the water drop and then gently let go. Performed correctly the coverslip will perfectly fall over the specimen.Draw the specimen as it appears in your viewing field under scanning, low and high power.
| Scanning
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Low Power
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High Power
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7. Staining a Specimen
1. Place one drop of stain (methylene blue) on the edge of the coverslip. Caution: Methylene Blue will stain clothes and skin!
2. Place the flat edge of a piece of paper towel on the opposite side of the coverlip. The paper towel will draw the water out from under the coverslip, and the cohesion of water will draw the stain under the slide.
3. 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 as needed, get a new piece of paper towel and add more stain until it does.
4. Be sure to wipe off the excess stain with a paper towel.Draw your specimen as it appears under low power. Used color pencils to show how the stain appears. It may appear darker or lighter in spots. Use shading to show darker and lighter spots.
| Scanning
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Low Power
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High Power
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8. Investigation of Pond Water & Microorganisms
Drawing Specimens
1.
Use pencil - you can erase and shade areas
2. All drawings should include
clear and proper labels (and be large enough to view details). Drawings should
be labeled with the specimen name and magnification.
3. Labels should be written
on the outside of the circle. The circle indicates the viewing field as seen through
the eyepiece, specimens should be drawn to scale - ie..if your specimen takes
up the whole viewing field, make sure your drawing reflects that
1. Prepare a wet mount of pond water - a sample of pond water is provided in a jar.
The best specimens usually come from the bottom and probably will contain chunks
of algae or other debris that you can see with your naked eye. (Be careful that
your slide isn't too thick)
2.
Use the microscope to focus on the slide - try different objectives, some may
be better than others for viewing the slide..
3.
Make three separate drawings below at different areas of the slide and at different
4. Obtain preserved slides of various microorganisms and specimens. Draw your specimens and label with the name of the specimen and the MAGNIFICATION
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9. Cheek Cell Smear
Finding human cells can be accomplished by scraping the inside of the cheek with a toothpick and rubbing this into a droplet of methylene blue to stain the cells of the cheek. Place a cover slip on the droplet. These cells will appear as light blue blobs with dark spots in the center, the nucleus and will be small at a 40x magnification. Create a wet mount of your cheek cells and find them using the high power (400x) objective. Draw your cells (at 400x) and label the cell membrane and the nucleus.
9. Investigation of Large Specimen
Light microscopes are only useful for viewing small thin specimens. In biology, you will perform dissections on larger specimens an may need to magnify the area of interest. In this situation, a stereoscope may be the best instrument. Stereoscopes present a larger field of viewing and handle depth much better than the light microscope. The drawback of the stereoscope is that it does not have a high magnification. Examine one of the stereoscopes in the room. They will be positioned around the room with specimens..
Name/Description of specimen(s) viewed: _________________________________________________________
What is the magnification(s) of the sterescope? _____________
Adjust the light settings. Some stereoscopes have a "Darkfield" setting or other light settings. Compare the way the specimen appears using different light settings. _____________________________________________________
10.
Measuring with a Microscope
Use a clear ruler to determine the width of the viewing field under the scanning objective. Position the ruler so that the millimeter marks are visible in your viewing field. Remember that there are 1000 micrometers in a millimeter.
Estimate the length (diameter) of your viewing field in micrometers (scanning ) _________
Repeat for low power _________________
You cannot use this method to determine the diameter under high power (try switching objectives). Instead you can use a mathematical proportion method to determine the diameter under high power.
What is the diameter (in micrometers) of your high power field _____________________
Sketch – with estimated dimensions for length & width (in microns). Indicate the length and width of an individual cork cell and the DIAMETER of viewing field under high power.
Slide Micrometers – obtain one of these items and place it on the stage. It is basically an itty bitty tiny ruler that you can see with both the high and low power objectives. The stage micrometers are marked with a label that says .01 mm. .01 millimeters = 10 microns
Use the micrometer to determine the field of view sizes in microns and millimeters.
Low Power ______ (microns, μm) _______ (millimeters, mm)
High Power ______ (microns. μm) _______ (millimeters, mm)
Determine the size of the AMEBA shown on the picture
....................................................................._______ μm _______ mm
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