Does reflected sunlight have the same effect as direct sun?
Because of all the different rays in sunlight I was wondering if the reflected light has the same quality for growing seedlings or does some of the invisible light not get reflected! What part of light does the plant use most? The spectrum colors of light is vast but what part does the plant use most? Is there a way to filter the best parts to reach the plant? Does the infra red or ultraviolet harm the plants? How do Reflections from a mirror compared in quality to reflected light from a white surface ?
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grrlgeek
- Senior Member
- Posts: 162
- Joined: Fri Aug 23, 2013 10:03 pm
- Location: Southern California Desert
Generally speaking, plants use the red spectrum for flowering, and the blue spectrum for leafy growth. They largely reject/reflect the green spectrum. Unless you have a high grade telescope mirror, Nothing is going to reflect 100%, although the mirror will reflect more of the spectrum but (for plant lighting purposes) less of the time and it will reflect at an angle based on the angle that the light hits it (the angles of incidence and of reflection). You can also burn a hole in the wall (ok, probably not, but try lighting a pile of leaves with a focused reflection from a mirror just for fun. ahhh... memories of a misspent youth) You would have to keep the mirror moving, like the collectors on a solar panel, unless you completely surround the plant in mirrors, or used a spherical mirror that would bounce light in multiple directions. Here's some math on that subject:
https://micro.magnet.fsu.edu/primer/ligh ... intro.html
https://physics.bu.edu/~duffy/PY106/Reflection.html
https://www.splung.com/content/sid/4/page/planemirrors
A white surface is going to reflect all colours of the spectrum, as would a mirror. But the difference is that if will diffuse the light in multiple directions, and it will do that all the time with whatever light is cast its way. Nothing, in my price range anyway, will replace direct sunlight. I'm not a physics geek, but what I'm gleaning from the science, is that more usable light for the whole plant, over the course of a day, can be had by painting the walls around it bright white.
https://en.wikipedia.org/wiki/Diffuse_reflection
Perhaps there's a scientist around here that could, ahem, shed more light
on the subject.
https://micro.magnet.fsu.edu/primer/ligh ... intro.html
https://physics.bu.edu/~duffy/PY106/Reflection.html
https://www.splung.com/content/sid/4/page/planemirrors
A white surface is going to reflect all colours of the spectrum, as would a mirror. But the difference is that if will diffuse the light in multiple directions, and it will do that all the time with whatever light is cast its way. Nothing, in my price range anyway, will replace direct sunlight. I'm not a physics geek, but what I'm gleaning from the science, is that more usable light for the whole plant, over the course of a day, can be had by painting the walls around it bright white.
https://en.wikipedia.org/wiki/Diffuse_reflection
Perhaps there's a scientist around here that could, ahem, shed more light
on the subject.-
IndyGerdener
- Green Thumb
- Posts: 392
- Joined: Thu Jun 21, 2012 12:32 pm
- Location: Greenwood, Indiana
If you have watched myth busters, they did a special about the sun reflecting to light a cave. They aimed a mirror at the sun and then bounced it all the way back to the rear of the room. This worked, but the light was reduced exponentially with every reflection in the room. This tells me that reflected light is not as good as direct light.
If we think about how this could be used in what we do, possibly we can use the reflected light to harden our plants one step at a time.
The other problem they had on mythbustets was keeping the sun aimed. It kept moving out of the mirror and they had to adjust the aim every 30 min. So I feel that would be your greatest problem with this type of idea. Maybe there is some way to overcome that.
Interesting thought though
If we think about how this could be used in what we do, possibly we can use the reflected light to harden our plants one step at a time.
The other problem they had on mythbustets was keeping the sun aimed. It kept moving out of the mirror and they had to adjust the aim every 30 min. So I feel that would be your greatest problem with this type of idea. Maybe there is some way to overcome that.
Interesting thought though
For starting seedlings will reflected light keep plants from getting leggy? Or will they reach for the light source anyway but in an angular way. Will the seedlings get confused with light coming from all angles and distances? While that is a joke, is the question of legginess still valid?
In my basement under florescent lights the bulbs are kept at about an inch above the top of the seedlings to produce thicker stronger stems. Window sill plants tend to be a problem and it seems reflected light is diminished enough to also cause growth problems.
Good question about reflected light. No physics here to give a good opinion.
In my basement under florescent lights the bulbs are kept at about an inch above the top of the seedlings to produce thicker stronger stems. Window sill plants tend to be a problem and it seems reflected light is diminished enough to also cause growth problems.
Good question about reflected light. No physics here to give a good opinion.
I have several seedlings containers under 2 4 foot lights that I keep a foot above so I cover a bigger surface area so I leave them on 24 hours. It seems to work fine! If you light source is not real bright leave it on longer. If you have more plants that need light move the light up more away from the plants to cover a bigger area and simply leave it on longer!