Question

what is uses if lens

Answer 1

Convex lenses have a significant drawback when used in optical applications like binoculars and telescopes. Light is often passed through a convex lens incorrectly, causing the image to appear with incorrect colors. Concave lenses are used in binoculars and telescopes so what you see is the correct color.

Answer 2

There are many uses of lens.
For example in vehicles,
For saving, for eyes etc.