Question

The value of numerical aperture of the objective lens of a microscope is $1.25$. If light of wavelength $5000\mathring{\text{A}}$ is used, the minimum separation between two points, to be seen as distinct, will be :

• A. $0.38\mu \text{m}$
• B. $0.48\mu \text{m}$
• C. $0.24\mu \text{m}$
• D. $0.12\mu \text{m}$

Answer 1

The correct option is C $0.24\mu \text{m}$

The minimum separation between two points for a distinct image formed by microscope is given by,

$x=\frac{1.22\lambda }{2\mu sin\theta }$

$\text{Here,}\mu \sin \theta \to \text{Numerical aperature}$

$\Rightarrow x=\frac{1.22\times 5000}{2\times 1.25}=0.24\mu \text{m}$

Hence, option $\left(A\right)$ is correct.