Question

how will you decide whether a given piece of glass is a convex lena, concave lens or a plane glass plate?

Answer 1

Hold the given piece of glass over some printed matter.

(i)If the letters appear magnified,the given piece is a convex lens.

(ii)If the letters appear diminished,the given piece is a concave lens.

(iii)If the letters appear to be of the same size,then it is a plane glass piece.