The resolution power of a compound microscope is:

HP CHO -9 October 2022

Applied Microbiology & Infection control

Easy

Appeared in: HP CHO -9 October 2022

Explanation

The resolution power of a standard compound light microscope is limited to approximately 0.2 micrometers (µm) or 200 nanometers (nm).
This limit is primarily dictated by the wavelength of visible light (about 400-700 nm) and the numerical aperture of the objective lens.
Objects closer than 0.2 µm will appear as a single blurred image rather than two distinct points.
This level of resolution is sufficient to visualize most bacteria and eukaryotic cells but not smaller structures like viruses.

Option B: This value is incorrect. 0.2 millimeters is equal to 200 microns, which is a thousand times larger than the actual resolution of a light microscope.
Option C: This value represents a much higher resolution than what is achievable with a light microscope. An Angstrom is a very small unit (1 Å = 0.1 nm).
Option D: This is a macroscopic unit of measurement. 0.2 centimeters is equal to 2 millimeters, a distance easily visible to the naked eye.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Resolution power of a compound microscope as background academic context rather than a clinical decision trigger.
In a clinical laboratory, understanding microscope resolution is crucial for correctly identifying microorganisms. For example, bacteria (typically 0.5-5 µm) are visible with a light microscope, but viruses (typically 20-300 nm) are too small and require an electron microscope.
This knowledge helps nurses and lab technicians understand why certain diagnostic tests are used for specific pathogens (e.g., Gram stain for bacteria vs. electron microscopy or PCR for viruses).
What if? If a sample was suspected to contain a prion (a misfolded protein, much smaller than a virus), even an electron microscope might not be sufficient, and techniques like Western blotting or immunohistochemistry would be required for diagnosis.

How to Approach the Question

Identify the core concept: The question asks for the 'resolution power' of a 'compound microscope'.
Recall the fundamental limits of light microscopy. The resolution is limited by the wavelength of visible light.
Evaluate the units of the options: micron, millimeter, Angstrom, and centimeter. Recognize that microscopic resolution is measured in very small units.
Eliminate grossly incorrect options. Millimeters and centimeters are macroscopic units, making them highly unlikely answers for microscopic resolution.
Differentiate between the remaining small units. Recall that Angstroms are associated with electron microscopy (atomic level), while microns (micrometers) are used for light microscopy (cellular level).
Select the option that matches the known resolution limit of a light microscope, which is approximately 200 nm or 0.2 microns.

Concept Tested & Keywords

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