Question

प्राशीराप
मे
राजनैतिर सार्थयालिराजपामार्यपालिका
स्मा अपर है १​

Answer 1

A light ray can pass through a lens from either direction. Therefore, a lens has two principal foci.

For a convex lens, the first focal point is a point F1 on the principal axis of the lens such that the rays of light starting from it or passing through it, after refraction through lens, become parallel to the principal axis of the lens.