Assertion (A) : Köhler 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 plane of the specimen.
In the light of the above statements, choose the most appropriate answer from the options given below :
The question asks to evaluate two statements, Assertion (A) and Reason (R), regarding Köhler illumination in microscopy.
Evaluating Assertion (A)
Assertion (A) states: "Köhler illumination is designed to produce bright and uniform illumination."
- Köhler illumination is a standard technique in microscopy.
- Its primary goal is to achieve even and bright illumination across the entire field of view, optimizing image quality.
- Therefore, Assertion (A) is correct.
Evaluating Reason (R)
Reason (R) states: "It is a lighting system in which the condenser focuses the image of the light source directly onto the plane of the specimen."
- This description accurately defines critical illumination, not Köhler illumination.
- In critical illumination, the light source image is focused directly onto the specimen. This often leads to uneven illumination and glare from dust or imperfections on the light source.
- Köhler illumination involves focusing an image of the light source onto the condenser's aperture plane, and then using the condenser's field lens to create an image of the lamphouse aperture (or filament pattern) in the back focal plane of the objective, resulting in uniform specimen illumination.
- Therefore, Reason (R) is incorrect.
Conclusion
Since Assertion (A) is correct and Reason (R) is incorrect, the most appropriate choice is that (A) is correct but (R) is not correct.
Important Questions from Miscellaneous
- Which of the following relationships is/are not true?
(A). Most probable velocity = $\sqrt{\frac{2RT}{M}}$
(B). PV = $\frac{3}{2}kT$
(C). Compressibility factor Z = $\frac{pV}{nRT}$
(D). Average kinetic energy of gas = $\frac{1}{2}kT$
Choose the correct answer from the options given below - Match List-I with List-II
List-I List-II Electronic Configuration First Ionisation energy (kJ mol$^{-1}$) (A). ns$^2$ (I). 2100 (B). ns$^2$np$^1$ (II). 1400 (C). ns$^2$np$^3$ (III). 800 (D). ns$^2$np$^6$ (IV). 900
Choose the correct answer from the options given below: - The shielding constant of a 2p electron (calculated using Slater's rules) is
- Match List-I with List-II
List-I List-II Spectroscopy Property (A). Raman (I). Polarizability (B). FTIR (II). Dipole Moment (C). UV-Visible (III). Absorbance (D). NMR (IV). Spin
Choose the correct answer from the options given below: - The structure of protein comprises of:
(A). Primary structure of protein is associated with amino acids
(B). Secondary structure of protein is associated to peptides
(C). Tertiary structure of protein is associated with polypeptide chains
(D). Quaternary structure of protein is associated with polypeptide chains
Choose the correct answer from the options given below:
