Thank you, but I am unable to intuit the physicality of those pressure gradients and their wave length dependencies. I think I need to look up how scattering amplitudes are calculated to see the wave length dependencies for scattering. I don't recall it being done in my classical or quantum physics courses, a long long time ago, in a galaxy far far away. AG -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to email@example.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.