Objectives: Microscope

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After performing this activity, you should be able to:
1. handle the microscope properly;
2. identify the parts of the microscope;
3. describe what parts of the microscope can do;
4. prepare materials for microscope study;
5. focus the microscope properly;
6. compare the image of the object seen by the unaided eye and under the microscope; and 7. compute for the magnification of objects observed under the microscope. [pic]


1. Get the microscope from its box or the cabinet. Do this by grasping the curved arm with one hand and supporting the base with the other hand.

2. Carry it to your table or working place. Remember to always use both hands when carrying the microscope.

3. Put the microscope down gently on the laboratory table with its arm facing you. Place it about 7 centimeters away from the edge of the table.

4. Wipe with tissue paper or old t-shirt the metal parts of the microscope. Q1. What are the functions of the base and the arm of the microscope?

5. Figure 1 shows a light microscope that most schools have. Study and use this to locate different parts of the microscope.

6. Look for the revolving nosepiece. Note that objectives are attached it. You should know that there are lenses inside the objectives. Q2. What have you observed about the objectives?

Most schools have light microscopes with three objectives. Others have four. Usually, the shortest one marked 3x, 4x or 5x is called the scanner. The low power objective (LPO) is marked 10x or 12x while the high power objective (HPO) is marked 40x, 43x or 60x. The objectives magnify the object to be observed to a certain size as indicated by the 3x, 10x or 40x, etc. marks. If the longest objective of your microscope is marked 97x or 100x or OIO or the word “oil” on it, then it has an oil immersion objective (OIO). This objective is used to view bacteria, very small protists and fungi. The OIO requires the use of a special oil such as quality cedarwood oil or cargille’s immersion oil.

7. Find the coarse adjustment. Slowly turn it upwards, then downwards. Q3. What is accomplished by turning the coarse adjustment upwards? downwards?

8. Looking from the side of the microscope, raise the body tube. Then, turn the revolving nosepiece in any direction until the LPO is back in position. You will know an objective is in position when it clicks. Note that the revolving nosepiece makes possible the changing from one objective to another. Q4. What is the other function of the revolving nosepiece?

Q5. Which part connects the eyepiece to the revolving nosepiece with the objectives?

9. Locate the eyepiece. Notice also that it is marked with a number and an x. Know that the eyepiece further magnifies the image of the object that has been magnified by the objective. If the eyepiece is cloudy or dusty, wipe it gently with a piece of lens paper.

10. Look through the eyepiece. Do you see anything?

11. Now, locate the mirror. Then, position the microscope towards diffused light from the windows or ceiling light. Look through the eyepiece and with the concave mirror (with depression) facing up, move it until you see a bright circle of light.The bright circle of light is called the field of view of the microscope. Adjust the position of the mirror so that it is not glaring to the eyes. Practice viewing through the microscope using both eyes open. This will reduce eyestrain. Q6. What are the two functions of the eyepiece?

Q7. Describe the function of the mirror.

12. Locate the diaphragm. While looking into the eyepiece, rotate the diaphragm to the next opening. Continue to do so until the original opening you used is back under the hole in the stage. Q8. What do you notice as you change the diaphragm openings? Q9. What can you infer as to the function of the diaphragm?

13. Find the inclination joint.
Q10. What parts of the microscope are being connected by...
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