Spherical vs. Parabolic Lens

[G1SG2]

Okay, so when we do problems in optics, we assume a parabolic surface, because we are working with spherical surfaces, right? Or do I have it the other way around? What's the difference between the two, and how does that affect the properties/function of the lens/mirrors? Thanks.

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[Seraph 84]

You'll only need to know properties of spherical lenses for the MCAT. I've never worked a problem that involved a parabolic lens. All the thin lenses that you analyze have spherical surfaces - their curvatures have radii which determine the focal point.

A parabolic surface would make the lens a lot more complicated. You probably wouldn't be able to use the same thin lens equations because the lens surface is no longer spherical and doesn't have a fixed radius of curvature.

If you want to visually compare the two surfaces, compare the y = x^2 graph to a semicircle and you'll see the difference.

 

[thebillsfan]

would i be correct in saying that we're using spherical surfaces because they're easier to compute with, but in reality a parabolic surface is more ideal b/c it reduces spherical abberation?