A convex lens and a convex mirror, made of glass $\left(\mu =3/2\right)$ initially placed in air, are immersed in water, $\left(\mu =4/3\right)$ then :         

Focal length of the mirror increases, that of the lens decreases

Focal length of the mirror decreases, that of the lens increases

Focal length of the mirror remains same, that of the lens increases

Focal length of the mirror remains same, that of the lens also remains same