Question

state the condition when a lens has both its focal length equal

Answer 1

if the medium on both sides of the lens is same,its first and second focal lengths are equal .

Answer 2

Answer:

:

Focal length is the distance between focal point and center of lens. Focal point is the point where parallel rays meet after passing through the lens. If the medium on both sides is same, the focal point will be the same and hence, same focal lengths