b
(b)Velocity of efflux when the hole is at depth h, \(v = \sqrt {2gh} \)
Rate of flow of water from square hole
\({Q_1} = {a_1}{v_1}\)= \({L^2}\sqrt {2gy} \)
Rate of flow of water from circular hole
\({Q_2} = {a_2}{v_2}\)= \(\pi {R^2}\sqrt {2g(4y)} \)
According to problem \({Q_1} = {Q_2}\)
==> \({L^2}\sqrt {2gy} = \pi {R^2}\sqrt {2g(4y)} \) \( \Rightarrow \)\(R = \frac{L}{{\sqrt {2\pi } }}\)