Eyepiece Graticule Calibration for Cell Measurement Steps:

• Stage micrometer: 100 divisions = 10 mm, so 1 division = 0.1 mm = 100 μm.
• Graticule shown (100 divisions) covers 12 stage divisions, so graticule total = 12 × 100 μm = 1200 μm.
• 1 graticule division = 1200 μm / 100 = 12 μm.
• Cell spans 5 graticule divisions (per diagram), so length = 5 × 12 μm = 60 μm. Why C is correct:
• 60 μm equals the calibrated length using the formula: actual size = (graticule units × stage division size) / graticule units per stage span. Why the others are wrong:
• A: 2.5 μm ignores graticule divisions spanned by cell.
• B: 3 μm misapplies stage scale without calibration factor.
• D: 3 mm confuses total stage length with cell measurement. Final answer: C