Question

The image of a point source S' lying at a distance b from a transparent sphere is formed by a small diaphragm only by rays close to the optical axis (Fig. 120).

Where will the image be after the sphere is cut into two parts perpendicular to the horizontal axis, and the plane surface of the left half is silvered?

Answer 1

It follows from symmetry considerations that the image of the point source S will also be

at a distance b from the sphere, but on the opposite side (Fig. 241).