What kind of a spherical mirror must be used and what must be its radius of curvature in order to get an erect image `(1)/(5)` as large as an object placed 15 cm in front of it ?

Explanation

m = `(1)/(5) , u = - 15 cm , m = (f)/(f - u)`
`(1)/(5) = (f)/(f - 15) " " 5f = f - 15 " " f= - 3.75` cm
Negative sign shows that the mirror is concave. R = 2f = 2 `xx 3.75 = 7.5` cm