Microbiology LAB Exam with Frequently Asked Questions and Verified Answers

Microbiology LAB Exam with Frequently Asked Questions and Verified Answers What is the primary purpose of an achromatic lens in a light microscope? A) Increase magnification without improving resolution B) Eliminate chromatic and spherical aberrations C) Increase specimen brightness D) Stain the specimen automatically Correct Answer: B) Eliminate chromatic and spherical aberrations Rationale: Achromatic lenses are designed to correct color distortion (chromatic aberration) and reduce spherical aberration, producing a clearer and sharper image. What is the role of immersion oil in light microscopy at 100x objective? A) To stain bacterial cells B) To increase numerical aperture by reducing light refraction C) To preserve the specimen D) To fix bacterial cells to the slide Correct Answer: B) To increase numerical aperture by reducing light refraction Rationale: Immersion oil has a refractive index similar to glass, minimizing light refraction and increasing resolution when used with the oil immersion objective. Which microscope component is primarily adjusted to optimize contrast and resolution? A) Eyepiece B) Objective lens only C) Condenser D) Stage clips Correct Answer: C) Condenser Rationale: The condenser focuses light onto the specimen, and its proper adjustment improves illumination, contrast, and resolution.