"misswizz" wrote in message
ups.com...
Hey shaniya here.

Thank you vey much for your reply.

I was wondering if you could explain to me the difference between the
wavelengths of blue light and sunlight.
Answer to this question would be highly appreciated.
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I will try to do so, if you will explain to me what "Hey shaniya" means.

Sunlight is a mixture of colours, from ultra-violet (which you cannot see,
but which you can certainly detect and measure with the appropriate
instruments), through violet, blue, green, yellow, orange, red, and then to
infra-red. Infra-red is also invisible to the human eye, but (like
ultra-violet) can be detected and measured using the appropriate
instruments. The fact that white light is a mixture of all the main colours
explains why you see the various colours of the rainbow when a beam of white
light is passed through a prism. It is also the underlying reason why you
see "all the colours of the rainbow" when you look at a rainbow. Indirectly,
it also is part of the explanation of why the sky is blue, and the sunset
red.

Blue light is just one of the constituent colours of white light. The blue
plastic that you have put over one of your pots of radish seedlings has the
effect of blocking the red, yellow and much of the green light from the sun,
while it is transparent to the blue light. That is why you can still see
objects by looking through the plastic, but they all seem blue. Your radish
seedlings will receive all the blue-light constuent of the sunlight, but the
other colours will be blocked. Because the red and yellow light have been
blocked by the blue plastic, the seedlings in this pot are, in fact,
receiving less sunlight energy than the seedlings that you have exposed to
direct sunlight. Does this matter?

Red light has a wavelength of around 800nm, while blue light is around
400nm. The shorter the wavelength, the higher the energy of the individual
photon. An individual photon of blue light has approximately twice the amout
of energy that an individual photon of red light has. For some types of
photosynthesis in some types of plant, the red photon simply does not have
sufficient energy to initiate a chemical reaction, while the higher energy
of a blue photon does produce photosynthesis. If this is the case with
radishes (and I do not know whether it is), removing the red and yellow
light by use of your blue plastic should (theoretically) have no effect on
the growth of the seedlings. All that would matter in such a case is "how
much blue light the plant receives".

Richard Chambers Leeds UK.