Microscopy Resolution · Histology

The 'angular aperture' ($\theta$) in the calculation of NA refers to:

  1. The angle of the microscope stand
  2. The half-angle of the cone of light entering the objective lens
  3. The angle at which the observer views the specimen through the eyepiece
  4. The tilt of the specimen slide
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Correct answer: The half-angle of the cone of light entering the objective lens

The angular aperture is the maximum angle at which the objective lens can pick up light from the specimen. A wider cone (larger angle) allows for more diffraction orders to be collected, enhancing resolution.

Difficulty: Medium Question 13 of 20

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