A convex lens of focal length 15 cm produces a magnification of +4. The object is placed
a) at a distance of 15 cm
b) between 15 cm and 30 cm
c) at less than 15 cm
d) beyond 30 cm

Focal length = 15cm

Magnification = +4

Type of lens : convex

We have to find distance of object..

★ Lateral Magnification :

m = v/u

4 = v/u

v = 4u

★ Lens Formula :-

→ 1/v - 1/u = 1/f

Focal length of convex lens is taken +ve and that for concave lens is taken -ve.

→ 1/4u - 1/u = 1/15

→ -3/4u = 1/15

→ u = -45/4

→ u = -11.25 cm

∴ (D) is the correct answer