Question

where plano convex and concave lens are used

Answer 1

Plano-convex lenses are optical Lenses with a positive focal length. These lenses are used in a wide range of applications . It can be used to focus, collect, and collimate light. And also, these lenses are useful as simple imaging lenses for systems where image quality requirement is not too critical. These are used in telescopes, microscopes, collimators, optical transceivers and magnifiers etc.
On the other hand, uses of concave lens: For a myopic eye, In spectacles, In door hole lens, In telescope, In binoculars