Question

what is nature of magnification of concave and convex lenses?
what sign + or - will be on it? ​

Answer 1

For a concave lens, the “magnification” is always less than 1. In other words, the image is actually smaller than the object. This is the formula for themagnification (M) involving the focal length (f) of the lens: M = f/(f - object distance). In fact, that's the same for concave lenses and convex lenses.