[1] https://upload.wikimedia.org/wikipedia/commons/f/f6/Chloroph...
Also, there are multiple chlorophyll molecules, with slightly different spectra. Lots of fun stuff in this field.
when I went to farming school around 1998 - 2000 we once visited a local commercial greenhouse and one thing I remember is they told me they used to have chemicals (plant hormones possibly?) that they sprayed on the leaves of flower plants to stop them from stretching and develop a more compact form, but had stopped doing that and now just lowered the temperature in the room a couple of hours before sunrise to get the same effect.
In fact I previously used only 6000K LED strips (in an insulated box so no other light at all) on cycad and other seeds and got very healthy plants.
I think the key for commercial applications like vertical farms is to optimise energy use by trying not to waste electricity on wavelengths that won't do much to boost production.
Natural sunlight sanitizes because the radiation from the sun includes UV-* band radiation that is sufficient to radiate organic cells at this distance.
EM light/radiation intensity decreases as a function of the square of the distance from the light source (though what about superfluidic wave functions and accretion discs and microscopic black hole interiors (every 30km by one estimate) and Lagrangian points,).
"Inverse-square law" https://en.wikipedia.org/wiki/Inverse-square_law
Ultraviolet: https://en.m.wikipedia.org/wiki/Ultraviolet
> Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For humans, suntan and sunburn are familiar effects of exposure of the skin to UV light, along with an increased risk of skin cancer. The amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere. [2] More energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground. [3] However, ultraviolet light (specifically, UVB) is also responsible for the formation of vitamin D in most land vertebrates, including humans. [4] The UV spectrum, thus, has effects both beneficial and harmful to life.
Ultraviolet > Solar ultraviolet: https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet
> The atmosphere blocks about 77% of the Sun's UV, when the Sun is highest in the sky (at zenith), with absorption increasing at shorter UV wavelengths. At ground level with the sun at zenith, sunlight is 44% visible light, 3% ultraviolet, and the remainder infrared. [23][24] Of the ultraviolet radiation that reaches the Earth's surface, more than 95% is the longer wavelengths of UVA, with the small remainder UVB. Almost no UVC reaches the Earth's surface. [25] The fraction of UVB which remains in UV radiation after passing through the atmosphere is heavily dependent on cloud cover and atmospheric conditions. On "partly cloudy" days, [...]
(Infrared light ~is heat.
There's usually plenty of waste heat from mechanical friction, exothermic chemical processes with gravity, lossy AC-DC conversion, and electronic components that waste energy/electron_field_disturbance//thermions/heat like steaming water towers sans superconducting channels wide enough for electrons to not start tunneling out without a ground or a negative)
Ultraviolet > Human health-related effects > harmful effects https://en.wikipedia.org/wiki/Ultraviolet#Harmful_effects
UV-A and UV-B protective eyewear (U6 polycarbonate) can be purchased in bulk. https://www.amazon.com/s?k=uvb+ansi+z87+glasses+20+pairs