Question

The focal length of a concave mirror is 30cm. find the position of the object in front of the mirror , so that the image is three times the size of the object . ​

Answer 1

sol :- As the object in front of the mirror it is real and object the magnified image formed by concave mirror can be inserted (i.e ... real ) or erect (i.e ... virtual ) , so there are two possibilities.

(a) of the image is inverted (i.e real )

m = f /f - u => -3 = - 30 / -30 - z

=> u = - 40 cm

object must be at a distance of 40cm in

front of the mirror ( in between C and F ).

(b) if the image is erect ( i.e virtual)

m = f / f - u => 3 = - 30 /-30 - u

=> u = - 20 cm

object must be at distance of 20 cm in front of the mirror (in between F and P )