Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Koehler illumination is designed to produce bright and uniform illumination.
Reason (R): It is a lighting system in which the condenser focuses the image of the light source directly onto the specimen plane.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Koehler illumination → uniform light; light source not imaged on specimen.

Answer 1

The Correct Option is C

Concept: Koehler illumination is an optical technique used in microscopy to provide even illumination and high image contrast.

Step 1: Understanding Assertion (A).
Koehler illumination ensures:
• Uniform brightness across the field of view
• Elimination of glare and uneven lighting Thus, Assertion (A) is correct.

Step 2: Understanding Reason (R).
In Koehler illumination:
• The condenser focuses light onto the specimen
• However, the image of the light source is NOT focused on the specimen plane
• Instead, the light source is focused at the condenser aperture plane Thus, Reason (R) is incorrect.

Step 3: Logical evaluation.
Assertion is correct but Reason is incorrect. Final Conclusion:
Hence, the correct answer is option (3).