Calibration

What and why calibrate?

Recall that there are times where we need to measure the size of the microscope specimen. 

The small ruler that is used to measure the size of specimens is the eyepiece graticule, which lies in one of the eyepiece.

There are 100 divisions to this eyepiece graticule, but you will notice that there are no units on it. As such, before using it, we need to calibrate it using the stage micrometer (which has a precisely marked scale, where one division = 0.01mm)

By calibration, it simply means to find the measurement of 1 eyepiece unit at the current magnification. 

Remember that since the eyepiece graticule is 'before' the magnification lenses, it always looks the same regardless which magnification lens you use, as such, it needs to be re-calibrated whenever you change the objective lens, i.e., the magnification! (or you could use math to do the conversion!)

👁️‍🗨️ Watch this video (until 2:51) that shows how calibration is done:

Try the following simulation to calibrate the eyepiece graticule!