"Joe" wrote in message

Wrong again Mooron. Subs have viewing ports not lenses unless the are
concave or convex and reshape light transmitted thru them. .

Um, wrong again.

Only reason sunglasses have Lenses is because they are a rip off of the
proper name of perscription lenses used in standard eye glasses that
predate sunglasses. The proper terms is sunglasses or filters, not
sunlenses.

And again.

You should try learning before spouting off.

So should you, Joe. Lenses do a wide variety of things, including causing
light to diverge or converge, as you've implied. They occasionally do
nothing at all, such as with plano lenses. They can act as light filters,
as with sunglass lenses. They can neither diverge nor converge light, but
bend light, aka prismatic lenses. They can affect color vision, aka colored
filter lenses. They can simply reduce light level without coloration, aka
neutral density lenses. And the list goes on, and they are ALL properly
called lenses.

So are those glass or resin plano "windows" in portholes, etc. It's a
traditional term in those cases.

Max