"Actually I do not think that it quite happens this way if you mean that
the coatings are going going to increase the transmission of light
through the lens to 99%. No coating can make glass transmit more light.
... If my memory of my old text book on the physics of optics is correct
anti-reflective coatings work by creating a duplicate of the reflected
light component that is 180 degrees out of phase and which cancels the
reflection. So if a lens element, uncoated, passes 970f the light
hitting its surface, with an anti-reflective coating it will pass the
same amount minus any light absorbed or reflected by the coating. The
previously reflected 3 0lare just disappears, speaking in gross terms.
All the action takes place between the glass surface and the inside
surface of the coating. So in multicoating the first layer acts on the
reflection from glass surface and each coating layer after that acts on
the reflection from the layer next to it."
This still isn't correct. Believe it or not, the light that isn't
reflected ACTUALLY ENTERS THE LENS. The coating doesn't just reduce
reflection; it actually INCREASES the transmission.
Furthermore, multi-coatings act "as a whole," despite the fact that this
seems to contradict "common-sense" notions of cause and effect.
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