# Talk:Lens (geometry)

## Redirect to lens (optics)?

I don't see a reason for this article to be separate. It basically says, in geometry a lens is a figure having the shape of an optical lens. Oleg Alexandrov 15:03, 17 Jun 2005 (UTC)

• No it doesn't. And that statement is clearly untrue. As the pictures in lens (optics) demonstrate, many optical lenses are not, in fact, this geometrical shape at all. Uncle G 18:17, 2005 Jun 17 (UTC)
• I did see the picture. That's why I wrote "shape of an optical lens" and not "shape of the optical lens". Oleg Alexandrov 23:49, 17 Jun 2005 (UTC)
• You wrote "the shape", implying one shape. Uncle G 00:51, 2005 Jun 18 (UTC)

I think either this article should be expanded (so that one understands what the motivation for this is), or otherwise it should be redirected to lens (optics) which is a very nice article. Oleg Alexandrov 15:03, 17 Jun 2005 (UTC)

• A redirect would be wrong. The geometric figure has nothing to do with the optical device. Uncle G 18:17, 2005 Jun 17 (UTC)
• Well, that's a strong statement. A geometrical lens is just a particular type of an optical lens. But either way, I understand your point. However, the way this article looks now, it has no reason to exist. More material should be added explaining what that geometrical lens thing is about. Oleg Alexandrov 23:49, 17 Jun 2005 (UTC)
• A geometrical lens is just a particular type of an optical lens. — False. A geometrical lens is a shape, a mathematical abstraction. An optical lens is a device, made of glass or some such. The one is not a subset of the other. They are two wholly different things, as different from each other as cone (geometry) and ice cream cone are different from each other. More material should be added — ... as, indeed, the stub notice on the article says. There's no need for you to keep repeating what the stub notice says, as if it were something heretofore unknown. If you like, you can do what it says. References that can be used have already been supplied. Uncle G 00:51, 2005 Jun 18 (UTC)
You are right, one is a geometric shape, and the other is an actual piece of glass. I was trying to object your point that they have nothing in common. Of course they have a lot in common; one can make a piece of glass in the shape described in this article, that one is then called an optical lens.
And you are right that everybody is welcome to expand that article. I just thought that since you went to great length to create this article, you could as well make it longer than once sentence. Oleg Alexandrov 01:34, 18 Jun 2005 (UTC)

## area of lens

How can be computed the area of lens? I know there are some formulas, but can anyone put them in the text please? --Excaliburo 15:27, 27 December 2005 (UTC)