Answer:
The refractive index of the outer coating is 1.52.
Explanation:
Refractive index of interior part, n' = 1.97
critical angle, C = 50.4°
Let the refractive index of the coating is n.
Use the Snell's law,
[tex]n\times sin r = n'\times sinC\\\\n\times sin 90 = 1.97 \times sin 50.4\\\\n = 1.52[/tex]