- Measure the diameter of the field of view. Once you determine the size of the field of
view for any combination of ocular and objective lenses, you can determine the size of
any structure within that field.
a. Rotate the 4x objective into position and remove the letter slide.
b. Place a clear ruler on the stage and focus on its edge.
c. The distance between two lines on the ruler is 1mm. With this knowledge, what is
the diameter (mm) of the field of view?
3mm
d. Convert this measurement to micrometers (µm), a more commonly used unit of
measurement in microscopy.
e. Measure the diameters of the field of view for the 10x and 40x objectives, and
enter all three in the spaces below to be used for future reference:
4x = 3 µm 10x = 2 µm 40x = 1 µm
f. What is the relationship between the size of the field of view and magnification?
5. Determine spatial relationships. The depth of field is the thickness of the specimen that
may be seen in focus at one time. Because the depth of focus is very short in the
compound microscope, focus up and down to clearly view all planes of a specimen.
a. Rotate the 4x objective into position and remove the ruler. Take a prepared slide
of crossed threads, wipe it with a kimwipe, and place the slide on the stage.
Center the slide so that the region where the two threads cross is in the center of
the stage opening.
b. Focus on the region where the threads cross.
Are both threads in focus at the same time?
c. Rotate the 10x objective into position and focus on the cross.
