Question

Two poles are separated by a distance of $3.14\, m$. The resolving power of human eye is $1$ minute of an arc. The maximum distance from which he can identify the two poles distinctly is

• A. 10.8 km
• B. 5.4 km
• C. 188 m
• D. 376 m

Answer 1

Answer: (A)

10.8 km

Answer 2

Given the lateral separation of the poles $d =3.14\, m$
The resolving power of the eye is
$\theta=1 \min =\pi /(60 \times 180)$ rad
The maximum distance from which poles are distinctly visible is
$D = d / \theta$
$\Rightarrow D =(3.14 \times 60 \times 180) / \pi$
$=10800 \,m =10.8 \,km$