The diameter of the nozzle (d) for maximum transmission of power is given by (where D = Diameter of pipe, f = Darcy’s coefficient of friction for pipe and $$l$$ = Length of pipe)

A. $${\text{d}} = {\left( {\frac{{{{\text{D}}^5}}}{{8{\text{f}}l}}} \right)^{\frac{1}{2}}}$$

B. $${\text{d}} = {\left( {\frac{{{{\text{D}}^5}}}{{8{\text{f}}l}}} \right)^{\frac{1}{3}}}$$

C. $${\text{d}} = {\left( {\frac{{{{\text{D}}^5}}}{{8{\text{f}}l}}} \right)^{\frac{1}{4}}}$$

D. $${\text{d}} = {\left( {\frac{{{{\text{D}}^5}}}{{8{\text{f}}l}}} \right)^{\frac{1}{5}}}$$

Answer: Option C