Answer:
1.414
Explanation:
the critical angle is the minimum angle of incidence in the denser medium for which the angle of refraction in rarer medium is 90 degree.
the relation between the refractive index and critical angle is given by
n = 1 / Sin i
n = 1 / Sin 45
n = 1.414
thus, the refractive index of the material medium is 1.414.