Question

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

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

Answer 1

Answer: (A)

The correct option is A $0.24\mu m$
Numerical aperature of the microscope is given as
$NA=.\frac{0.61\lambda }{d}$
Where $d=$ minimum sparation between two points to be seen as distinct
$d=\frac{0.61\lambda }{NA}=\frac{\left(0.61\right)\times \left(5000x10m^{-10}\right)}{1.25}$
$=2.4\times {10}^{-7}m$
$=0.24\mu m$