Answer:
65.48°
Explanation:
Using Snell's law as:
[tex]n_i\times {sin\theta_i}={n_r}\times{sin\theta_r}[/tex]
Where,
[tex]{\theta_i}[/tex] is the angle of incidence (? )
[tex]{\theta_r}[/tex] is the angle of refraction ( 30.0° )
[tex]{n_r}[/tex] is the refractive index of the refraction medium (diamond, n=2.42)
[tex]{n_i}[/tex] is the refractive index of the incidence medium (water, n=1.33)
Hence,
[tex]1.33\times {sin\theta_i}={2.42}\times{sin30^0}[/tex]
Angle of incidence = [tex]sin^{-1}0.9098[/tex] = 65.48°