Question

Sun glasses have curved surfaces but they don't have power. Why?​

Answer 1

Answer:

This means that the outer and inner surfaces of the sunglasses have the same radius of curvature. This indicates that the two surfaces run parallel to each other and the magnification produced by the outer convex surface gets neutralized by the magnification produced by the inner concave surface and hence produces a net magnification or minification of zero, and the light passes through it and emerges out parallel to the incident ray. Since the power of a lens arises from the difference in the radii of curvature of either spherical surfaces, we can say that the power of the sunglasses are zero for this reason.