Penetration in the context of light usually refers to high energy focused forms such as laser. Light for photosynthesis is either absorbed, reflected or even refracted when it hits plant material. If the light we were using to grow plants had high penetration that would be akin to making grilled greens on the barbq. Actually, that is the principle of how infrared grills work.
Instead of penetration, effective range/draw/throw of a light source may be more correct and is simple to figure out with a PAR meter. Take light source, measure a distance away and take a PPFD reading. Go a bit further away and take another measurement. The difference in length is the 'throw distance' and the difference in PPFD is the photon count 'range' that your leaves will receive.
Another quirk in the efficiency equation is the wavelengths produced by the light source. Depending on the wavelength photons may carry different amounts energy. Longer wavelengths, eg. red, have less energy than lower wavelengths such as those in the blue regions. That is photon to photon. Plants are photon counters needing ~8 photons to power a reaction.
Generally speaking, higher wavelengths are better for organisms that haven't specifically adapted to higher energy (shorter) wavelengths. The problem comes with managing the free energy when the photon gets absorbed; shorter wavelength high energy photons require more effort from the organism. Some wavelengths in the UV range are highly destructive. Photosynthesis has a wonderful way of managing the excess energy by retransmitting it through chlorophyll
fluorescence allowing other parts of the plant to use the photons. Unfortunately it isn't very efficient and most of the light energy absorbed by plants is wasted as heat.
And here is where I shamelessly plug my opinion of ~400 umols consisting of 10% warm white + 90% 600-730nm being optimal for photosynthesis.
