Question

Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm. Approximately, what is the maximum distance at which these dots can be resolved by the eye? [Take wave length of light =500 nm]

• A. 10 m
• B. 5 m
• C. 15 m
• D. None of these

Answer 1

The correct option is B 5 m

We have, $\frac{y}{D}\ge 1.22\frac{\lambda }{d}$

$\Rightarrow D\le \frac{yd}{\left(1.22\right)\lambda }=\frac{{10}^{-3}\times 3\times {10}^{-3}}{\left(1.22\right)\times 5\times {10}^{-7}}$

$=\frac{30}{6.1}\approx 5m$

$\therefore D_{max}=5m$