How do I use a calibrated reticle to measure an object viewed with the microscope?

BIOL 1406

PreLab 4.2

How do I use a calibrated reticle to measure an object viewed with the microscope?

Once you have calibrated your reticle, you can measure objects using the reticle and then convert the arbitrary “reticle units” into standard units of measurement, such as micrometers. To do this, simply multiply the measurement in r.u.’s by the number of µm/r.u. for the particular objective you used.

In PreLab 4.1, you calibrated the reticle for 2 different microscopes, A and B:

Microscope and Objective	Calibration of reticle (µm / r.u.)
A with 5X objective	20.0
B with 4X objective	28.6
A with 10X objective	10.0
B with 40X objective	2.86

Your Turn
Assume that you have measured the diameter of six diatoms with microscope A (above) using the 10X objective. The six diatoms measured 2, 2.5, 4, 5, 6, and 6.5 reticle units. What were the diameters of the diatoms in µm’s? If using Microscope A and the 10X objective:
2 r.u. = µm	Hint	Check your answer.
2.5 r.u. = µm	Hint	Check your answer.
4 r.u. = µm	Hint	Check your answer.
5 r.u. = µm	Hint	Check your answer.
6 r.u. = µm	Hint	Check your answer.
6.5 r.u. = µm	Hint	Check your answer.

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