Question

If we cut a convex lens half along the principle axis what will be focal length and how it is different from the lens which is cut perpendicular to the axis? ARE THIS QUESTION ARE EASY OR DIFFICULT?

Answer 1

Questions like this are easy if you apply lens maker's formulae logically. In the first case, the lenses have the same radii even after cutting, so, there will be no change in focal length. However, in the second case, the radius of curvature of one half (R2) becomes infinity (as the half becomes flat). So, the focal length will be effected.