Question:medium

The ratio of resolving powers of an optical microscope for two wavelengths $\lambda_1 = 4000 \mathring A$ and $\lambda_2 = 6000 \mathring A$ is :

Updated On: May 22, 2026
  • 9 : 4
  • 3 : 2
  • 16 : 81
  • 8 : 27
Show Solution

The Correct Option is B

Solution and Explanation

The resolving power of an optical microscope is determined by its ability to distinguish between two closely spaced objects. The resolving power \( R \) is inversely proportional to the wavelength \(\lambda\) used for observation. Mathematically, it can be given by:

R \propto \frac{1}{\lambda}

Given two wavelengths, \(\lambda_1 = 4000 \mathring{A}\) and \(\lambda_2 = 6000 \mathring{A}\), the ratio of resolving powers \(R_1\) to \(R_2\) is:


\frac{R_1}{R_2} = \frac{\lambda_2}{\lambda_1}

Substituting the given values:

\frac{R_1}{R_2} = \frac{6000}{4000} = \frac{3}{2}

Thus, the ratio of the resolving powers is 3:2, which corresponds to the correct answer from the given options.

Conclusion: The correct answer is 3:2. This choice is justified because resolving power increases with a decrease in the wavelength, thus for smaller wavelength (\(4000 \mathring{A}\)), the resolving power is higher.

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