hey can u explain something about luminous intensity?

Question

1. what is the reason why Candela (cd) is used as a unit in luminous intensity?

2. which will provide greater efficiency, a 50watt tungsten filament bulb?or a 40watt flourescent lamp

tnx a lot!

Answer 1

1) See this link for the origina of the SI unit the 'Candela'.
http://en.wikipedia.org/wiki/Candela#Origin

2) The 50 Watt Tungsten filament bulb is about 10% efficient in producing light - in fact it produces more heat than light.

The 40 Watt Flourescent lamp (known as a gas discharge lamp) is around 15-18% efficient, so I would go with the gas discharge lamp.