Given

n_xy = 2/3

Where n_xy= refraction index of a medium ‘X’ with respect to medium ‘Y’

We know,

Substituting given value in the equation:

. . . . . . . . equation 1

It is also given that, n_yz = 4/3

Where n_yz = the refractive index of medium ‘Y’ with respect to medium ‘Z’

Substituting the given value in formula:

_{. . . . . . . . . . .} equation 2

Refractive index of medium ‘Z’ with respect to medium ‘X’ will be given by:

Substituting values from equation 1 and 2

Refractive index of medium ‘Z’ with respect to medium ‘X’ is 9/8