Focal Length of a Plano Convex Lens

[bgq]

Hi,

The focal length of the Plano-Convex lens as calculated by the lens maker equation: Does it work when light crosses the lens from the convex side, planar side, or both?

Thanks.

 

[jtbell]

Calculate it both ways: using R₁ for the convex side and R₂ for the plane side; and using R₁ for the plane side and R₂ for the convex side. Does it make a difference in the result?

Hint: watch out for the + and - signs!

 

[bgq]

Calculate it both ways: using R₁ for the convex side and R₂ for the plane side; and using R₁ for the plane side and R₂ for the convex side. Does it make a difference in the result?

Hint: watch out for the + and - signs!

Thank you very much, It is clear now that the focal length is the same.