Does the picture change if we turn a thin lens around

[HastiM]

Hello,

suppose we are given a thin lens and consider an image of some object formed by that lens. I am wondering what would happen to the image if the thin lens is flipped around (180 degrees)? Of course, if the lens is perfectly symmetric -like for a bi-konvex lens- then the picture should not change at all. But what if the lens is not symmetric, e.g. as for a plano-convex lens?

I think that the light beams should bend differently (but not very much differently). Is that true? The reason why I expect the light beams to bend differently, is because the light beams are refracted twice by the lens. First, when they enter the lens, and second when they leave the lens. So, if we change the order of these two refractions, the light beams should bend differently in general. But on the other hand, because the lens is thin, the light beams would behave almost the same. Please tell me if I am wrong...

Best

 

[Khashishi]

Yes, the image would change. The purpose of different shaped lenses is to reduce the aberrations in the image caused by the lenses. A rule of thumb is that you don't want the light rays to hit the surface of the lens at too large an angle from the surface normal. Aberrations get bad when the ray hits the surface at a shallow angle (and you also have a lot of reflection). So, if you have a plano-convex lens, you want the plane side on the side that the light is converging more sharply.
I found this image:

at https://github.com/OpenLabTools/OpenLabTools/wiki/Optical-Setup

 

[HastiM]

Thank you very much! :-)