When an object is placed at a distance of `60 cm` from a convex spherical mirror, the magnification produced is `1//2`. Where should the object be placed to get a magnification of `1//3` ?

Answer

`- 120 cm`

Explanation

Here, `mu_1 = -60 cm, m_1 = (1)/(2)`
`u_2 = ? M_2 = (1)/(3)`
If `f` is focal length of convex mirror, then from
`m = (f)/(f - u) , (1)/(2) = (f)/(f + 60)`….(i)
`(1)/(3) = (f)/(f + u_2)` ….(ii)
From (i), `2f = f + 60, f = 60 cm`
From (ii), `f + u_2 = 3 f`
`u_2 = 2 f = 2 xx 60 = 120 cm`.