For example, an
incandescent lamp of 150W produces 2,850 lumens
of visible light and 11,970 mW of radiation usable
by the plants. The ratio of 11,970 divided by 2,850
equals 4.2 mW/lm, the conversion factor for that
lamp. Table 6–1 on the next page gives energy
values and conversion factors for several lamp
types