1. BIO130 Lab 1 Exercise 3 The Microscope
Parts of the Microscope, Light Adjustment, & Diopter

2. Measuring Field Diameter Using the Stage Micrometer:
1. Insure that left ocular lens is turned fully counterclockwise
(Lens should be as tall as it can be)
2. Focus on the stage micrometer
3. Measure the diameter (widest part) of the field of view using the tiny millimeter ruler of the stage micrometer using only your left eye in the left ocular
40X Magnification

3. 100X Magnification
Read off where the ruler ends on the other side: this one looks like 1.745mm Each scope is a little different
Line up the 0.0 line on the edge of the visible field: the zeros will no longer be visible

4. 400X Magnification

5. Using field diameter to determine the size of an object
Using field diameter to determine the size of an object specimen feature or cell:
1. Know the field diameter of the objective lens you are looking through. (We measured this)
2. Center and focus the object.
3. “Guess” how many of that object would fit end to end across the diameter of the field. (Diameter = the widest part of the circle of light you see through the lens)
10X objective: diameter measured to be 1860µm
Looks like 2 would fit across
1860µm

6. Using field diameter to determine the size of an object
Using field diameter to determine the size of an object specimen feature or cell:
4. Divide the field diameter by the number of objects you think would fit across end to end to determine the size of one of the objects.
10X objective: diameter measured to be 1860µm
Looks like 2 would fit across
1860µm ÷ 2 = 930µm
1860µm

7. New object:
10X objective: diameter measured to be 1860µm
Looks like 4 would fit across
1860µm
1860µm ÷ 4 = 465µm
The green oval is approximately 465µm long

8. Which lens do I use?
The object is a fixed size, regardless of lens you should get the same answer!
Use the lens that allows you to see the whole object the best: big enough to guestimate how many fit across the diameter, not too magnified that you cannot see the whole object in the same field.

9. 10X objective: diameter measured to be 1860µm
Looks like 4 would fit across
1860µm ÷ 4 = 465µm
1860µm
40X objective: diameter measured to be 465µm
Looks like 1 would fit across
465µm ÷ 1 = 465µm
465µm
This object (green oval) is 465µm: you should get approximately the same answer which ever lens you use.

10. Dogfish Placoid Scale Measure one diamond 4X objective (40X)

12. Dinoflagellate Don’t cut off his tails! 4X objective (40X)

13. Red Tide

14. Large irregular shaped cells: look like a ruffled sunny side up egg
Human Cheek Cell
4X objective
(40X)
Large irregular shaped cells: look like a ruffled sunny side up egg
10X objective
(100X)
40X objective
(400X)

15. Tiny red dots, even with the 40X objective: guestimate carefully!
Human Blood Smear
4X objective
(40X)
Tiny red dots, even with the 40X objective: guestimate carefully!
10X objective
(100X)
40X objective
(400X)
WBC
RBC

16. Dogfish Placoid Scale Dinoflagellate Human Cheek Cell
Human Blood Smear
WBC
RBC