A thin convex lens made from crown glass μ =3/2 has focal length f. When it is measured in two different liquids having refractive indices 4/3 and 5/3 , it has the focal lengths f1 and f2 respectively. The correct relation between the focal lengths is:
(a) f1 = f2 < f
(b) f1 > f and f2 becomes negative
(c) f2 > f and f1 becomes negative
(d) f1 and f2 both become negative
