Find the total magnification of your microscope. First, read the power inscribed on the eyepiece. You’ll find it marked as a number followed by an X, which stands for “times.” Record the eyepiece power.
Find the three barrel-shaped objective lenses near the microscope stage. Each will have a different power, which should be marked on the side of the lens. Record the power for each objective.
Find the total magnification for each objective lens by multiplying the power of the eyepiece by the power of the objective.
Lowest Magnification: Eyepiece x Lowest power objective = ________X
Medium Magnification: Eyepiece x Medium power objective = ________X
Highest Magnification: Eyepiece x Highest power objective = ________X
Set the microscope to its lowest magnification. Slide the plastic metric ruler onto the stage and focus the microscope on the millimeter divisions. How many millimeters fit across the circle of light you see (the field of view)? This measurement is the field diameter. Record the field diameter in millimeters.
Repeat this process for medium magnification.
Repeat once more for the highest magnification. What do you notice?
The highest magnification may be tricky to measure because the field of view will probably be less than one millimeter in diameter—too small to directly measure with your ruler. To get a usable reading, move the ruler back and forth a bit to estimate the fraction of a millimeter that fits across the diameter, or use the measurements you’ve already made along with this handy bit of math:
What happens to the field diameter as the magnification increases? This inverse proportional relationship tells us something important about the relationship of magnification to field diameter.