BACKGROUND INFO - Continued
Three types of light sources were utilised during the
experiments. One was a natural
light source; the other two were artificial sources.
All of them produce different amounts of light colours. Plants are able
to utilise some colours better than others (see figure).
Green and yellow are less important to plants then most since plants
reflect green and yellow light, which is why most plants appear to be green.
Light from the blue/indigo and red/orange ranges provide plants with the
most benefits. Blue light is
responsible for vegetation (i.e. leaf) growth.
Red light, when combined with blue light, encourages floral activity.
This is a natural light source. It
has a perfect balance of all the colours of the visible spectrum.
Sunlight originates from the sun. The
sun has many different layers. The
photosphere is the brightest of all its layers, and thus, is the part of the sun
that we usually observe. However,
when a total eclipse occurs, the photosphere is covered and the other parts of
the sun are visible.
Many people are familiar with this kind of lighting.
This kind of artificial lighting produces much red-range light and
infrared radiation, but very little blue-range light.
In other words, they have a high red to blue ratio.
Because of the amount of infrared radiation produced, incandescent bulbs
must be placed a fairly far distance from any plant.
Incandescent bulbs are very simple mechanisms.
Incandescent bulbs usually last for approximately 1000 hours.
These were the earliest used fluorescent tubes.
They produce much light in the blue range but hardly any in the red
range. In other words, they have a
high blue to red ratio. Fluorescent lights work on a fairly simple basis.
First, electrons race from two electrodes at the ends of the tubes, which
produces ultra-violet radiation. The
phosphor coating in the tube’s inner wall converts this into visible light.
Fluorescent bulbs are less expensive then incandescent bulbs in the long
run. First of all, they are about
three times as energy-efficient as regular incandescent bulbs.
On top of that, they have a longer life.
Fluorescent bulbs last for approximately 10 thousand hours, while
incandescent bulbs, as mentioned before, last for approximately 10 hundred
hours.
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