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

Question

$\begin{array}{1 1} (1) 8:27 \\ (2) 9:4 \\ (3) 3:2 \\ (4) 16:81 \end{array}$