a. Medium 1 is air. The refractive index of air is 1.0003. Refractive index is a measure of the bending of a ray of light when passing from one medium to another. If i is the angle of incidence of a ray in vacuum and r is the angle of refraction, the refractive index n is defined as the ratio of the sine angle of incidence to the sine of the angle of refraction; that is, n= sin i/ sin r. Refractive index may also be given by the velocity of light in medium 1 divided by the velocity of light in medium 2.
b. In this case the refractive index = sin 72.5/sin 39.6
= 1.4962
but n = x/ 1.0003 = 1.4962
Therefore; x = 1.4967
Hence the refractive index of medium 2 is 1.4967.
I therefore think that medium 2 is toluene; since it has a similar refractive index.