Q.

A convex mirror of radius of curvature 30 cm forms an image that is half the size of the object. The object distance is               [2024]

1 -15 cm  
2 45 cm  
3 -45 cm  
4 15 cm    

Ans.

(1)       

             Given R = 30 cm

              ⇒f=R2=+15 cm

             Magnification (m) = ±1/2

             For convex mirror, virtual image is formed for real object, therefore, m is +ve

             The mirror formula,

              1v+1u=1f⇒v=ufu-f

              Magnification, m=-vu=-ufu(u-f)=ff-u

             12=ff-u=1515-u⇒u=-15 cm