Question

what is the main structural difference between a convex lens and concave lens

Answer 1

Convex lenses are thicker at the middle. Rays of light that pass through the lens are brought closer together (they converge). A convex lens is a converging lens. When parallel rays of light pass through a convex lens, the refracted rays converge at the focalpoint.

Answer 2

see if you want to remember then remember that concave keyword:cave right?so cave is deep inside correct?so concave lens is deep inside in structure and the outer one is convex.Let me know if i am helpful