An incident ray strikes a boundary at a 72.5-degree angle, resulting in an angle of refraction of 39.6 degrees. the index of refraction of the first medium is 1.0003. what is medium 1? what is medium 2?

Refractive index is the ration of sin i to sin r where i is the incident angle and r is the refraction angle. 
Therefore, refractive index = sin 79.5 / sin 39.6
                                           = 1.542
The refractive index may be given by the ratio of refractive index of medium 2 to refractive index of medium 1. 
Therefore, 1.542 = n/1.0003
                            n = 1.5425
                               ≈ 1.54
Medium 2 is sodium chloride, refractive index of 1.54

 

Iwannasay c is the most accurate