Calibrating eyepiece graticule using stage micrometer at ×100 magnification Steps:

• Identify stage division size: 0.1 mm, corresponding to 100 eyepiece units in the diagram.
• Convert to µm: 0.1 × 1000 = 100 µm (real stage distance).
• Divide by eyepiece units: 100 / 100 = 1 µm per unit (image plane size).
• Adjust for magnification: 1 / 100 = 0.01 µm (actual real size per unit).

Why C is correct:

• It follows the calibration formula: (stage size in mm × 1000) / eyepiece units / magnification, yielding real size in µm from the magnified image.

Why the others are wrong:

• A: Uses extraneous "100 by 0.1" step and misapplies multiplications, inflating the value.
• B: Converts and divides by units but skips magnification adjustment, overestimating real size.
• D: Applies incorrect divisions without proper conversion or magnification factor, yielding tiny erroneous value.

Final answer: C