Illumination
119
E
5m
x
x-
Lamp at each intersection
χ
χ
48
lamps inali
40
m
(a)
X
X
X
66 lamps
in all
X
X
Jörn
\~\
1
|
1
3^m
(b)
Figure
7.21
calculations it must give an original light input which exceeds that at
the end
of
the design life.
It is now necessary to examine the numbers and arranagement of
lamps by which the required illuminance may be provided.
Data
for
gas filled tungsten filament lamps is as follows:
Power, watts
Total output, lumens
60
576
100
1135
200
2600
300
4140
500
7500
Since
a
60 w
lamp gives
576
lumens,
to
provide 260000 lumens
would require 260000/576
=
452 lamps.
9m
Ceiling
200 Lx
A
2001 x
(a)
3.75 m
40
Lx
3.75 m
3.75 m
Working
plane
A