At what distance from a convex mirror of focal length 2.5 m should a boy stand so that his image has a height equal to half the original height ? The principal axis is perpendicular to the height.

Explanation

We have
`m = -(upsilon)/(u) = (1)/(2)`
or , `upsilon = (u)/(2).`
Also, `(1)/(u) + (1)/(upsilon) = (1)/(f)`
or , `(1)/(u) + (1)/(-u//2) = (1)/(2.5m)`
or `- (1)/(u) = (1)/(2.5 m)`
or u = - 2.5m.