Correct Answer - Option 3 : Lumens/watt
Luminous efficiency: It is also known as radiant efficiency. It is defined as the ratio of energy radiated in the form of light, produces sensation of vision to the total energy radiated out by the luminous body.
Radiant efficiency = energy radiated in the form of light / total energy radiated by the body
Lamp efficiency is measured in lumen/watt.
Important Points:
|
Lamp
|
Lamp efficiency
|
|
Carbon filament lamp
|
3 – 4.5 lumen/watt
|
|
Osmium filament lamp
|
5 lumen/watt
|
|
Tantalum filament lamp
|
2 lumen/watt
|
|
Tungsten filament lamp
|
18 lumen/watt
|
|
Carbon arc lamp
|
9-12 lumen/watt
|
|
LED lamp
|
10 - 110 lumen/watt
|
|
Neon discharge lamp
|
15 – 40 lumen/watt
|
|
Sodium vapor lamp
|
100–200 lumen/watt
|
|
Mercury vapor lamp
|
≈ 100 lumen/watt
|
|
Fluorescent lamp
|
50 - 100 lumen/watt
|
|
Incandescent lamp
|
4 – 17 lumen/watt
|
