Calibrating microscope eyepiece graticule with stage micrometer

Steps:

• Eyepiece graticule is a ruled scale in the eyepiece for estimating specimen size under magnification.
• Stage micrometer is a slide with a precise, known scale (e.g., 0.01 mm divisions) placed on the microscope stage.
• Aligning the stage micrometer's scale with the eyepiece graticule under the same magnification calibrates graticule units to actual lengths.
• Evaluate statements: 1 incorrect (requires prior calibration for cells); 2 correct (primary purpose); 3 correct (enables accurate real-size conversion post-calibration).

Why B is correct:

• Stage micrometer's known scale (definition: standardized ruler slide) calibrates eyepiece graticule for indirect, accurate measurements, including statement 3's implied use.

Why the others are wrong:

• A: Includes 1, which falsely claims direct measurement without calibration.
• C: Omits 2 and 3, ignoring core calibration function.
• D: Excludes 3, missing full utility in measurement setup.

Final answer: B