\(n_1 \sin(\theta_1)\)  = \(n_2 \sin(\theta_2\)

BUT, n = \(\frac{c}{v}\), where c is the speed of light in vacuum (approximately equal to the speed of light in air) and v is the speed of light in the medium.

For air, n\(_1\) = \(\frac{3 \times 10^8}{3 \times 10^8}\) = 1

For glass, n\(_2\) = \(\frac{3 \times 10^8}{1.8 \times 10^8}\) ≈ 1.667

Applying snell's law: \(n_1 \sin(\theta_1)\)  = \(n_2 \sin(\theta_2)\) = \(1 \sin(\theta_1)\)  = 1.667 sin(30) = 0.83335

 Thus, the sine of the angle of incidence is ≈ 0.8