Re: luminous efficiency

[Larry Woolf <larry.woolf@GAT.COM>]

I should have compared the output in lumens (not power dissipated in the
filament) to the ratio of D*L, so here's a new table:

25W     235 lumens              Lumens ratio=1  D*L = 0.168             D*L Ratio = 1
75W     1190 lumens             Lumens ratio=5.1        D*L = 0.292             D*L Ratio = 1.7
100W    1750 lumens             Lumens ratio=7.4        D*L = 0.371             D*L Ratio = 2.2
200W    4010 lumens     Lumens ratio=17 D*L = 0.734             D*L Ratio = 4.4

So I should have written in my previous email:
However, the total visible light output increases to a significant extent
because of the increase in emitting surface area of the filament, which is
proportional to diameter*length. From the calculation below, it appears that
about 35% of the light emission increase results from the increase in
emitting area, the remainder then is due to an increase in filament
temperature (or emissivity change).

(The data on lumens, filament diameter, and length that I have used are from
a GE Booklet entitled "Incandescent Lamps," with a number on the back cover:
TP-110R2 (5/84))