The image of an object placed in air formed by a convex refracting surface is at a distance of 10 m behind the surface. The image is real and is at \(\frac{2^{rd}}3\) of the distance of the object from the surface. The wavelength of light inside the surface is \(\frac 23\) times the wavelength in air. The radius of the curved surface is \(\frac x{13}\) m. the value of 'x' is...........
