# water column of height  7 cm. If refractive index of water is 1.269 1.286 1.259 1.310

$\\\frac{\lambda _{glass}}{6}=\frac{\lambda _{water}}{7}\\ \frac{v_{glass}}{6f}=\frac{v_{water}}{7f}\\ \frac{v_{glass}}{6c}=\frac{v_{water}}{7c}\\ \frac{\mu _{water}}{6}=\frac{\mu _{glass}}{7}\\ \mu _{water}=\mu _{glass}\times \frac{6}{7}\\ \mu _{water}=1.52\times \frac{6}{7}\\ \mu _{water}=1.3$