If that's right, as another layman (person ) I've been under the same misconception - I thought divergence was any "spread" of the beam.one thing i'd like to point out as a layman. i thought 'divergence' means the entire cone of light.
But then it was pointed out to me that 'divergence' is really just the whitish bright spot in the middle and the outer green light is 'atmospheric refraction'.
i don't personally want to call it refraction because the area above the water is also 'refraction' so i think it makes the terms confusing.. so i'm going to call it 'spread'.
So i think one bit of conversation with Sandor (in my case) might have been that i was saying divergence to mean the whole cone and maybe he was thinking i was just talking about the bright spot in the middle?
so i'm wondering if your sentence there should be changed to "divergence and spread" ??
Having said that, in one of my questions to Sandor I asked him to explain the splodges of green light across the white board. Still didn't get an answer.