These units easily provide over 2000
lumens per square foot.As tubes age they become less
efficient. On the average, they lose 25% of
light they were rated for after about a year
of use. Lights which are turned on and off a
lot wear out faster. Three to six inch
sections on both sides of the tube dull out
from deposits after a short term of use.
Growers figure the effective length of a 4 ft
tube as 3 feet 4 inches and of an 8 ft tube
as 7 feet.
Light Spectrums and Photosynthesis
Each source of light has a characteristic
spectrum, which is caused by the varying
wave lengths of light therein. Fluorescents
and other electric lights emit different
shades of light. To our eyes midday
summer sunlight looks neutral,
incandescent lights have a reddish tint,
fluorescents vary in spectrum according to
their type, MH lamps a have a blue
coolness to them, and HPS lamps look
pink-amber.
To produce chlorophyll, plants need
light from specific spectrums, (TABLE 1)
mainly red and blue. This is called the
chloroplast light spectrum. Once the
chlorophyll is produced, a slightly different