a)
[tex]\begin{gathered} n1sin(\theta i)=n2sin(\theta r) \\ n2=\frac{n1sin(\theta i)}{sin(\theta r)} \\ where: \\ \theta r=180-90-65=25 \\ so: \\ n2=\frac{sin(65)}{sin(25)} \\ n2=2.14 \end{gathered}[/tex]b)
[tex]\begin{gathered} \theta_B=tan^{-1}(\frac{n2}{n1}) \\ \theta_B=tan^{-1}(\frac{1.33}{1}) \\ \theta_B\approx53.06^{\circ} \end{gathered}[/tex]