Name: _________________________
Mark: _____/19
Measuring with a Microscope Lab
Introduction
Microscopes help scientists see really small things. In addition to helping scientists observe details
about specimen, scientists also use microscopes to estimate the size of things. This can sometimes be
challenging given the fact that the objects are small.
Purpose
1. To learn how to measure and estimate the size of objects using a compound light microscope.
2. Measure the diameter of your LOW power field of view.
3. Measure the diameter of your HIGH power field of view.
Materials
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

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Microscope
Calculator
Ruler
Prepared slides
Procedure
1. Obtain a microscope. Carry it with both hands to your lab bench. Plug it in and turn on the
light to full power.
2. Under LOW power, place a clear plastic ruler on the stage and focus it so that it looks like the
diagram below (remember to focus using the coarse adjustment first, then use the fine
adjustment).
Empty area of field
mm marking on ruler
3. Count the lines/marks of the ruler to measure the diameter (the imaginary line across the
middle) of your field of view. Record that number below.
4. Sometimes you will be asked to estimate the size of things in micrometers (um). Estimate the
diameter of your field of view using the information below.
1 millimeter (mm) = 1000 micrometers (um)
Microscopes LOW power field of view in mm = ______________
Microscopes LOW power field of view in um = ______________
© The Seismic Scientist – Measuring with a Microscope Lab
1
Name: _________________________
Mark: _____/19
You cannot use this method to determine the diameter HIGH power. Students quickly realize that
HIGH power magnifies the object so much that it takes up the entire field of view. To estimate the size
of things under HIGH power, the following mathematical proportion is used.
𝐻𝑖𝑔ℎ 𝑝𝑜𝑤𝑒𝑟 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 (𝑢𝑚)
𝑙𝑜𝑤 𝑝𝑜𝑤𝑒𝑟 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 (𝑜𝑛 𝑡ℎ𝑒 𝑠𝑖𝑑𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑜𝑏𝑗𝑒𝑐𝑡𝑖𝑣𝑒 𝑙𝑒𝑛𝑠)
=
𝐿𝑜𝑤 𝑝𝑜𝑤𝑒𝑟 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 (𝑢𝑚) ℎ𝑖𝑔ℎ 𝑝𝑜𝑤𝑒𝑟 𝑚𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 (𝑜𝑛 𝑡ℎ𝑒 𝑠𝑖𝑑𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑜𝑏𝑗𝑒𝑐𝑡𝑖𝑣𝑒 𝑙𝑒𝑛𝑠)
5. Use the formula from above to calculate the HIGH power diameter in um. Plug in an “x” for
HIGH power diameter and solve. You already calculated low power in um so you can just plug
that value into your formula. Check your objective lens (LOW and HIGH power) to determine
the magnification for each.
𝑥
=
High power diameter (um) = ______________
6. Fill in the chart below using the prepared slides. View all the slides under LOW power.
Complete column 1 with the names of each slide viewed. Estimate the size first in mm (column
2), then convert to um (column 3).
Slide Name
Size in mm
© The Seismic Scientist – Measuring with a Microscope Lab
Size in um
2