Question

Which has more luminous efficiency?

• A. A $40W$ bulb
• B. A $40W$ fluorescent tube
• C. Both have same
• D. Cannot say

Answer 1

Answer: (B)

A $40W$ fluorescent tube

Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power, measured in lumens per watt in SI.Luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency.

A 40 W40 W bulb has luminous efficacy of 9 lm/W9 lm/W,whereas a 40 W40 W fluorescent tube has a luminous efficacy of 59 lm/W59 lm/W

Hence a 40 W40 W fluorescent tube has more luminous efficiency.