Introduction to Microscopes and Microscope techniques Lab.docx

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					                                   Introduction to Microscopes and Microscope techniques Lab:
Purpose:
To learn the parts of a microscope
To learn to properly handle and focus a microscope
To compare an object viewed with a microscope to that object viewed with the unaided eye
To compare images under low, medium and high power
To determine the magnification, diameter and area of the field of view of a microscope
To prepare a wet mount slide and practice staining techniques
To learn how to draw and label proper scientific drawings

Materials:
Letter e from newsprint
Prepared animal cells
Prepared plant cells
Onion skin cells
Human cheek cells
Microscope
Blank slides
Cover slips
Petri dish
Eye dropper
Blank paper
Pencil
Transparent Ruler
Iodine stain
Methylene blue stain

Procedures:

A. Letter “e:
1. Cut out a single letter “e” (lowercase) from a newspaper or magazine.
2. Place 2 drops of water on a slide. And place your letter “e” on the water.
3. Bring the edge of a coverslip up to the water at a 45 degree angle and gently drop it onto the slide. If air bubbles are present,
gently push down on the coverslip with a probe to remove. If excess water is present on the slide (coverslip floats), place the edge of
a paper towel next to the cover slip to soak it up.
4. Focus the letter “e” on low power and draw a proper scientific sketch of what you see. Label a) ink, b) paper fibers, and c) air
bubbles on your drawing.
5. Repeat step 4 for the other powers of magnification. You should have different sketches for your letter “e” when finished.

*Be sure to label your drawings with the power of magnification
*Line up your circles (drawings) one under another in a column
B. Onion cells:
1. Peel off a piece of the thin inside skin of the onion.
2. Place the skin in the middle of the microscope slide.
3. Using the eye dropper, place 1 or 2 drops of iodine stain onto the skin.
4. Bring the edge of a coverslip up to the iodine stain at a 45 degree angle and gently drop it onto the slide. If air bubbles are
present, gently push down on the coverslip with a probe to remove. If excess liquid is present on the slide (coverslip floats), place
the edge of a paper towel next to the cover slip to soak it up.
4. Focus the specimen on low power and draw a proper scientific sketch of what you see. Label a) Cell wall, b) Cell membrane, c)
nucleus, d) nucleolus, e) cytoplasm on your drawings.
5. Make labeled drawings for what you see under the other powers of magnification. You should have 3 different drawings for the
onion cells.

*Be sure to label your drawings with the power of magnification
*Line up your circles (drawings) one under another in a column



C. Cheek cells:
1. Place a drop of water on a microscope slide.
2. Use the flat edge of a toothpick to gently scrape the inside of your cheek.
3. Gently swirl that end of the toothpick into the drop of water to release your cells onto the slide.
3. Using the eye dropper, place a small drop of methylene blue stain onto the drop of water and cheek cells.
4. Bring the edge of a coverslip up to the stain at a 45 degree angle and gently drop it onto the slide. If air bubbles are present,
gently push down on the coverslip with a probe to remove. If excess liquid is present on the slide (coverslip floats), place the edge of
a paper towel next to the cover slip to soak it up.
5. Focus the specimen on medium power and draw a proper scientific sketch of what you see. Label:
a) Cell membrane, b) nucleus, c) nucleolus, d) cytoplasm on your drawing.
6. Make a labeled drawing for what you see under the high power of magnification. You should have 2 different drawings for the
onion cells.

*Be sure to label your drawings with the power of magnification
*Line up your circles (drawings) one under another in a column




Observation, analysis and conclusion questions:

1. What is the estimated actual size of one of the onion cells you examined?
2. What is the estimated size of one of the cheek cells you examined?
3. Why do we use stains when preparing slides for viewing?
4. What differences did you see between the plant and animal cells you looked at?
5. What aspects of the lab (techniques) did you have some difficulty with when following the procedures?
How to measuring field of view and estimate size of specimens:
1. With the low power objective in place, put a transparent ruler onto the stage.
2. Position the millimeter marks on the ruler immediately below the objective lens.
3. Using the coarse adjustment knob, focus on the marks of the ruler.
4. Move the ruler so that one of the millimeter markings is just at the edge of the field of view. Find the diameter by counting how
many millimeters take up the field of view.
5. Most high power lenses provide a field of view less than one millimeter, so the field of view beyond low power can be calculated
using the ratio of the other lenses to the low power magnification. Show your calculations.

Ratio = Magnification of high power objective
        Magnification of low power objective

6. Use the ratios to determine the field of view diameter under the higher power magnifications. Show your calculations.

Field diameter = field diameter (low power)
                           Ratio

7. Remove the ruler and replace it with a prepared slide.
8. Estimate the number of times the specimen could fit across the field of view.
9. Calculate the width of the specimen. Show your calculations.

Width of specimen = ______width of field of view________
                       Number of specimens across the field

*Be sure to label your drawings with the power of magnification
*Line up your circles (drawings) one under another in a column
*Remember to include units of measurement.

How to focus:
1. Start at low power.
2. Adjust the stage away from the objectives by using the coarse focus knob to lower it.
3. Place your slide onto the stage.
4. Adjust the light to the dim intensity.
5. Align your specimen in the center of the field of light.
6. Peer into the microscope and slowly use the coarse focus to bring the stage closer (raise it) to the objective until the specimen
comes into focus.
7. You may need to adjust the intensity of the light and/or use the fine focus to get a clearer image.
8. Turn the nosepiece to move to the next objective power magnification. Repeat steps as necessary.

How to make proper scientific drawings:
1. Using a petri dish, trace a circle on the left hand side of your blank paper.
2. Look through your microscope and draw a picture in your circle of what you see in your field of view as you examine your
specimen on the slide.
3. Title your diagram, using the name of the specimen and the part of the specimen you have drawn.. Make sure to underline your
title.
4. Label your diagram. Use a ruler to draw horizontal lines to the right of the diagram. Your labels are to be printed beside the lines
in an even column.
5. Include the total magnification below your diagram.

Total magnification = Ocular magnification x Objective magnification
*Be sure to label your drawings with the power of magnification
*Line up your circles (drawings) one under another in a column

				
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