Question

Match List I with List II

List I (Microscopy) & List II (Application)
A. Bright field & I. For observing the ultrastructural features of microorganisms
B. Dark field & II. For observing gross morphological features of microorganisms
C. Phase contrast & III. For observing characteristics in living state and in fluid suspension
D. Electron & IV. For observing the cellular structures in living cells of larger microorganisms

Choose the correct answer from the options given below:

• A. A-IV, B-III, C-I, D-II
• B. A-III, B-IV, C-I, D-II
• C. A-I, B-II, C-III, D-IV
• D. A-II, B-III, C-IV, D-I

Hint:

For spirochetes (e.g., Leptospira), think Dark Field. For internal organelles of living cells, think Phase Contrast. For viruses and membrane details, think Electron Microscopy.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Different microscopy techniques utilize distinct illumination sources, optical pathways, and physical principles to visualize microbiological specimens.
Choosing the correct method depends on whether the cells are stained or unstained, living or fixed, and the required resolution.
Detailed Explanation:
Let us match the microscopy type with its optimal application:
- A. Bright field microscopy: The standard light microscope where light passes directly through the specimen. It is best used to observe the gross morphological features (shape, size, and arrangement) of fixed, stained microorganisms. This matches with II. For observing gross morphological features of microorganisms.
- B. Dark field microscopy: Uses a darkfield condenser that blocks direct light, directing only oblique light rays onto the specimen. Only light reflected or scattered by the specimen enters the objective lens, producing a bright image against a black background. This is ideal for observing thin, highly motile organisms (like the spirochete Leptospira) in their living state and fluid suspensions. This matches with III. For observing characteristics in living state and in fluid suspension.
- C. Phase contrast microscopy: Converts subtle phase shifts in light passing through cellular structures of varying refractive indexes into changes in amplitude (brightness). This allows high-contrast imaging of internal cellular details in living, unstained cells. This matches with IV. For observing the cellular structures in living cells of larger microorganisms.
- D. Electron microscopy: Uses an electron beam instead of light, achieving high resolution down to the nanometer scale due to the short wavelength of electrons. It is essential for resolving viruses and cellular organelles. This matches with I. For observing the ultrastructural features of microorganisms.
Therefore, the correct matches are: A-II, B-III, C-IV, D-I.

Step 2: Final Answer:
The matching matches Option (D).