Someone with more direct experience may be able to give a better answer, but considering the matter from first principles, you need to know the emission wavelengths of the red, blue, and orange LEDs in that fixture. Then see how well those wavelengths match the peak
absorption wavelengths of chlorophyll. The seller provides the LED emission wavelengths:Â
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The red LEDs emit at 660 nm. Looking at
the graph, you can see that will be poorly absorbed by Chlorophyll b and only moderately absorbed by Chlorophyll a.
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The orange LEDs emit at 630 nm. That is close to the crossing points of the absorptions of C(a) and C(b) and so will be absorbed a little bit by both, but not very well by either.
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The blue LEDs emit at 450 nm. That is far from the peak of the blue part of the absorption curve of C(a), but is fairly close to the absorption peak of C(b), so at least there, it looks like most of the light will be of use.Â
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The white LEDs are primarily there for the psychological benefit of humans. If the only LEDs in use emit light completely absorbed by the plants, then the plants will appear black to the human eye. Some people find that disconcerting.
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Of course, the LEDs themselves do not emit only at the precise wavelength specified, but have some bandwidth of emission. The full-width half maximum (FWHM) for these LEDs is around 25 nm, I think, so matters aren't quite as bad as the foregoing would suggest. Still, it would be much better if you had LEDs emitting at 430 nm and 662 nm, and 453 nm and 642 nm, the blue and red absorption peaks of C(a) and C(b), respectively.
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That's for a start. Even if the wavelengths match, you still need to determine if that particular fixture provides sufficient lumens for healthy growth. Most people think in terms of lumens required from broad spectrum sources and that is not applicable to LEDs. If the LED emission wavelength precisely matches the Chlorophyll absorption peaks, much less total luminosity is required. I'm sure those studies have been done (though possibly not for peppers), but I don't know how to answer that part of the question without getting more quantitative and convolving the absorption curves with the broad spectrum source curve. This is where someone with direct experience could better contribute.
Having said all that, it probably doesn't really help you make a decision. The overlaps of emission and absorption are probably good enough that the plants will grow and possibly grow well, and the price seems right. I'm just pointing out there's a lot of room left for improvement in LED implementation.
