Question

X is thicker in the middle than at the edges, whereas, Y is thicker at the edges than in the middle. Identify ‘X’ and ‘Y’.

(a) X = concave lens; Y = convex lens

(b) X = convex lens; Y = concave lens

(c) X = plane lens; Y = convex lens

(d) X = concave lens; Y = plane lens

This question was posed to me in semester exam.

Origin of the question is Ray Optics topic in division Ray Optics and Optical Instruments of Physics – Class 12

Answer 1

The correct answer is (b) X = convex lens; Y = concave lens

Best explanation: When the lens is thicker in the middle than at the edges, then it is convex lens. When the lens is thicker at the edges than in the middle, then it is concave lens. Therefore, X = convex lens, and Y = concave lens.