Correct Answer - 5.14 cm ; convex, erect and virtual ; 10.28 cm
Here, `u = - 18 cm, v = 4 cm, f = ?, R = ?`
As `(1)/(f) = 1/u + (1)/(v), (1)/(f) = (1)/(-18) + 1/4 = (-2+9)/(36) = 7/36` or `f = 36/7 = 5.14 cm`
as f is +, therefore, mirror is convex. Image is virtual, erect and smaller in size.
`R = 2 f = 2 xx 5.14 = 10.28 cm`.