An electric lamp of 100 candela requires 0.5 W of energy per candela. Find the efficiency of this lamp if the mechanical equivalent of light is 0.00161 W/lumen. Calculate the amount of light energy in ergs emitted by the lamp every second.
Answer: η ≅ 4%
Explanation:
The light energy emitted by the lamp is approximately equal to 2 joules = 2 x 107 ergs.
