What is required for the maximum high tide to occur?.

Tides are very long waves that move across the oceans. They are caused by the gravitational forces exerted on the earth by the moon, and to a lesser extent, the sun. ... Because the gravitational pull of the moon is weaker on the far side of the Earth, inertia wins, the ocean bulges out and high tide occurs.

Explanation:

snell's law

refractve index = sin incidence / sin refraction