Question

The length of a stage micrometer is 1 mm and it is marked with 100 tic marks including 10 long tic marks with number labels (0.1, 0.2, 0.3, etc.). The eyepiece (ocular) graticule has 50 tic marks, with a longer tic mark at every 10th position (meaning there are 5 groups of 10 units = 50 eyepiece graticule units). When the stage micrometer under the 10x objective lens is lined up with the eyepiece graticule so that the tic marks all face the same way and the zeros start at the same vertical line, the 50th unit line on the eyepiece lines up with the 0.6 mm line on the stage micrometer. Determine the value of one eyepiece unit. How much is the measure of each eyepiece unit in microns?

Answer 1

The smallest division in eye piece graticule are referred to as small eyepiece units (SEU).

When eyepiece graticule and stage micrometer is aligned, so that the 0 values have superimposed, according to the given problem,

50 SEUs = 60 divisions on stage micrometer (since they superimpose on 0.6 long tic on stage micrometer)

Also, each division on stage micrometer = 10 micrometer (since the stage micrometer is 1mm from end to end)

Therefore 1 SEU = (60/50) ×10 micrometer = 12 micrometer/ micron

Thus each eyepiece unit is equal to 12 micron.