ANSWER
61.21°
EXPLANATION
The refractive index of water is n = 1.33
In this problem the light travels from water to diamond, so we have to find the angle from the vertical form,
[tex]\tan \theta p=\frac{n_{\text{diamond}}}{n_{\text{water}}}[/tex]Replacing the indices,
[tex]\tan \theta_p=\frac{2.42}{1.33}[/tex]And solving for θ,
[tex]\theta_p=\tan ^{-1}(\frac{2.42}{1.33})[/tex][tex]\theta_p\approx61.21[/tex]Brewster's angle is 61.21°
