MCQ
The ratio of resolving powers of an optical microscope for two wavelengths $\lambda_1 = 4000\,\mathring A$ and $\lambda_2 = 6000 \,\mathring A$ is
  • A
    $9:4$
  • $3:2$
  • C
    $16$$:81$
  • D
    $\;8:27$

Answer

Correct option: B.
$3:2$
b
The resolving power of an optical microscope,

$\mathrm{RP}=\frac{2 \mu \sin \theta}{\lambda}$

For wavelength ${\lambda _1} = 4000\,\mathop {\text{A}}\limits^o $, resolving power will be

$\mathrm{RP}_{1}=\frac{2 \mu \sin \theta}{4000}$  ..... $(i)$

For wavelength ${\lambda _2} = 6000\,\mathop {\text{A}}\limits^o $, resolving power will be

$\mathrm{RP}_{2}=\frac{2 \mu \sin \theta}{6000}$  ..... $(ii)$

On dividing eqn. $(i)$ by eqn. $(ii)$

$=\frac{\mathrm{RP}_{1}}{\mathrm{RP}_{2}}=\frac{6000}{4000}=\frac{3}{2}$

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