Optical path of a particular ray of light has travelled a distance of 3 cm in flint glass is same as that on travelling a distance ' $x$ ' cm through another medium. The value of ' $x$ ' is [refractive index of flint glass $=1 \cdot 6$, refractive index of another medium $=1.25]$

A string is under tension of 180 N and mass per unit length $2 \times 10^{-3} \mathrm{Kg} / \mathrm{m}$. It produces two consecutive resonant frequencies with a tuning fork, which are 375 Hz and 450 Hz . The mass of the string is

Two spheres of equal masses, one of which is a thin spherical shell and the other solid sphere, have the same moment of inertia about their respective diameters. The ratio of their radii is

Assuming the expression for the pressure exerted by the gas, it can be shown that pressure is