Download corkandlettere

Science 7
Name________________
Mrs. Shapiro
Group _______
Compound Light Microscope -Cork and Letter “e” Lab
Background:
The compound light microscope is an important scientific tool. It enables a person
to
observe things too small to be seen with the unaided eye. In many of the activities
in
this lab, you will use a compound microscope, a microscope having two lenses.
The
two lenses are the ONE eyepiece lens AND one of three the objective lenses. In
this
type of microscope, light passes through the specimen, or object being viewed.
One
lens, the objective, causes the light rays to coming from the specimen to spread
apart,
forming an enlarged image of the object. The second lens, the ocular, focuses and further enlarges the image.
Working with a compound microscope, you may use specimens that have been prepared in one of two ways. A
prepared slide is made to be permanent and can be purchased from a supply house. A wet mount slide is made
;/for temporary use and can be made and used during a single lab period.
Two principles involved when using the microscope are:
Magnification – the ability to enlarge and image
Resolution – the ability to produce a clear image
As magnification increases and light rays are scattered more, the resolution or distinctness of the image
decreases.
--------------------------------------------------------------------------------------------------------------------------------------Objectives (Purpose):
1. This lab should enable students to become familiar with the parts of the microscope and its proper use.
2. Review basic slide making techniques.
Materials:
Microscope
Microscope slide
Cover slip
Beaker of water
Pipette dropper
Newsprint
Colored thread
Colored Newsprint
Scissors
Pen & Pencil
Colored pencils
Lab Protocol
Hair samples
Procedure:
The microscope is an expensive, precision instrument. Handle it carefully!
Part One: Analysis
1. To know how to use the microscope, you must first be familiar with the parts of the microscope. Take a
few minutes using the labeled diagram to find all parts of the microscope.
2. Position the microscope with the arm of the microscope facing you. The base should be at least 10
centimeters from the edge of the desk.
3. Use LENS PAPER to clean the stage, and eyepiece.
4. Place the low power lens into position. Adjust the diaphragm so that the light is directed through one of
the apertures (holes) to the stage opening. It is best to start with a medium sized aperture and adjust as
needed.
1
Part One: PREPARED SLIDE-Cork cells
1. Place your prepared slide on the stage with the label facing you and secure it using the stage clips. Make
sure that the lowest power objective lens is clicked in place. ALWAYS START WITH LOW POWER
even in you want to see under high power!
2. Using the coarse adjustment, lower the objective lens as far as it will go down without hitting the cover
slip. Be sure to watch the lens as you lower the low power objective. Never lower the lens while
looking through the eyepiece.
3. Look through the eyepiece. Adjust the low power objective by turning the coarse adjustment toward
you. The cork sample will soon come into view. NOW….. carefully and slowly use the fine adjustment
until you achieve adequate focus.
4. After you have adequate focus under the lowest power, switch to the MEDIUM power objective. Readjust the focus using the fine focus knob. You may continue up to the highest power although it will be
difficult to see under the highest power.
5. Determine which power was the clearest and SKETCH what you see in the space below.
SKETCH of prepared slide of cork under (low, medium, high) power
Part Two: WET MOUNT SLIDE-the letter “e”
1. Prepare a wet mount slide of a newsprint lowercase letter “e”.
2. Rinse a microscope slide with water and wipe both sides with a clean soft cloth.
3. Hold the slide by the edges.
4. Obtain a dry cover slip from the supply area.
5. Cut a small piece of newsprint that contains a lowercase “e”. it should be an e from an article NOT a
headline.
6. Using a pipette dropper, place a drop of tap water from the beaker in the center of the slide.
7. Place the newsprint in the drop of water. Lower the cover slip over the top of the water drop and
newsprint. Be sure not to trap air bubbles under the cover slip.
8. Place your temporary wet mount on the stage of the microscope and position the letter “e” as you would
read it. Use stage clips to hold the slide in place.
9. Using the coarse adjustment, lower the power objective lens as far as it will go down without hitting the
cover slip. Be sure to watch the lens as you lower the low power objective. Never lower the lens while
looking through the eyepiece.
10. Look through the eyepiece. Adjust the low power objective by turning the coarse adjustment toward
you. The letter ”e” will soon come into view. Carefully use the fine adjustment until you achieve
adequate focus.
11. Draw what you see under 2 powers; you choose your best view.
12. Switch to a high power objective. Again, use fine adjustment to achieve adequate focus. Draw what you
see under high power. (See conclusion questions 7-10.)
2
Letter ”e” ________X
Letter ”e” ________X
Part Three: Color Newsprint
1. Using the same wet mount procedure in Part II, compare two different samples of colored newsprint.
2. Note the differences and similarities between the two samples.
Sample Color__________ ______X
Sample Color__________ _____X
Part Four: Colored Thread:
1. Select two different colors of thread. Cut a small piece of each and prepare a wet mount slide.
2. Be sure to position the two pieces in an “X” over each other.
3. Observe the threads under low and then high power.
4. Using the fine adjustment focus on the top thread first and then continue to focus in on the bottom
thread. Note the difference in focus as you change your depth of field.
Thread Top Focus ___________X
Thread Bottom Focus ___________X
3
Results Data:
Microscope Magnifications
Eye Piece (Ocular Lens)
Low Power Objective Lens
Medium Power Objective Lens
High Power Objective Lens
10
4
10
40
Observations:
Diagrams:
See attached diagrams
Total Magnification = Eye Piece X Objective Lens
Total Magnification Low Power =
Total Magnification Medium Power =
Total Magnification High Power =
-------------------------------------------------------------------------------------------------------------------------------Conclusion (Analysis & Interpretations): ANSWER on back of page 5
1. The low power objective is shorter than the high power objective. In what other way does the high
power objective differ from the low power objective?
2. What magnification is printed on the lens of the low power objective?
3. What power is the eyepiece?
4. What is the total low power magnification?
5. What is the total high power magnification?
6. What is seen through the eyepiece?
7. Describe the position of the letter “e” when it was first view through the eyepiece.
8. What happens to the “e” as you move it to the right?
9. What happens top the “e” as you push the slide away from you?
10. How does the area of the slide change when going from low to high power?
11. What happens to the focus (in general) as you change from low power to high power?
12. What did you observe about the colored newsprint as seen under the microscope?
13. In observing the colored thread how could you determine the slide had depth?
4
Reference Diagram:
5