Question

what could be the distance between the lens and paper when it was burned by the rays of sun, placed under a thin converging lens.​

Answer 1

Answer:

In the figure below parallel rays from sun (infinity) after passing through the convex lens are focused to a point F. This point is the focal point.

Therefore, distance between the lens and the paper; where a hole is burnt due to concentration of light rays (heat rays in this instance); is equal to the focal length of the lens.