Question

The luminous efficiency of a lamp is $51$$m{W}^{-1}$ and its luminous intensity is $35Cd$. The power of the lamp is

• A. $11$ $W$
• B. $22$ $W$
• C. $44$ $W$
• D. $88$ $W$

Answer 1

The correct option is D $88$ $W$

$1lumen=\frac{1}{4\pi }Cd$

$luminousefficiency=\frac{luminousflux}{power}$

$power=\frac{4\pi \times 35}{51}=88W$