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Measuring and Counting with a Light Microscope

Author(s): David R. Caprette, PhD

Using Volume to Estimate Depth

Another way to estimate vertical distance is to consider the volume of material under a cover slip. For example, suppose you have a square cover slip of 22 x 22 mm and you place it over a 40 µl drop of aqueous sample. One milliliter (1000 microliters) of pure water at standard temperature and pressure has a volume of 1 cubic centimeter, while a microliter has volume of one cubic millimeter. Forty microliters, therefore, have a volume of 40 cubic millimeters. The surface area under your cover slip is 484 sq. mm, so the space under your cover slip is 40 ÷ 484 = 0.082 mm. Assuming the liquid is spread out evenly under the cover slip and rounding to reflect precision, the space under the cover slip is 80 micrometers deep.