# A concave mirror of focal length f(in air) is immerssed in water $(\mu =\large\frac{4}{3} )$. The focal length of mirror in water will be

$(a)\;\frac{f}{3} \\ (b)\;\frac{4}{3} f \\ (c)\;\frac{3}{4} f \\ (d)\;f$

Focal length of either concave or convex mirrors do not depend on the refractive index of the surrounding medium. Hence the focal length of concave mirror remains the same.
Hence 'd' is the correct option

edited Jul 14, 2014