Question

when concave lens will behaviour like convex lens​

Answer 1

Answer:

Concave lens can behave as a convex lens when placed in a medium whose refractive index is greater than that of the material of which the concave lens is made. This is because the focal length of a concave lens is directly proportional to the refractive index of the medium (in which it is kept)

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Answer 2

Answer:

concave lens can behave as a convex lens when placed in a medium whose refractive index is greater than that of the material of which concave lens is made.