Question

under what condition will a thin lens have magnification -1 ​

Answer 1

Answer:A concave lens will have magnification always as -1

Explanation:u,v and f is always negative

Answer 2

Answer:

Magnification is not a property of a lens. It does confer power.

When a plane mirror produces a magnification of $+1$, the image size is equal to the size of the object.

Explanation:

Magnification is defined as the ratio of the image's height to the height of the corresponding object, or the distance between the object and its corresponding image distance. The signs of these quantities can be interpreted according to your preferred convention. Remember to stick to one definite convention and don't stray from it.

For lens of

a focal length f,

$\frac{1}{u} \frac{1}{v} \frac{1}{f}$

Where u = object's distance from the thin lens

v = Image distance from the thin lens.

Magnification, m=$\frac{v}{u}$= $\frac{h_{1} }{h_{0} }$ ;

m=$-1$