Magnification Formual For Lens

Lens-Maker's Formula|Magnification|Rules For Image Formation|OMR

Magnification of the lens is always positive for __

(a) The linear magnification of a concave lens is always positive. Why? (b) The linear magnification of a convex lens may be positive or negative. Why ?

Magnification by a lens of an object at distance 10 cm from it is -2. now a seconnd lens is placed exactly at the same positon where first was kept, without changing the distance between object and lens. The magnification by this second lens is -3. Now both the lenses are kept in contact at the same place. what will be the new magnification ?

For which position of the object, magnification of convex lens is -1.(minus one) ?

A screen beaming areal image of magnification formed by a convex lens is moved through a distance x. The objectis the moved until a new image of magnification is formedon the screen. The focal length of the lens is :