When the ray of light from underwater strikes the smooth surface of the water at an angle of incidence greater than the critical angle, then total internal reflection occurs (TIR). The ray of light must pass from the denser medium to rarer medium.
When the angle of incidence is equal to 90, the angle formed is called critical angle.
In this case, the diagram (D) shows the angle of incidence greater than the critical angle and hence TIR occurs.
Well my thinking is that the lighter the slower the water evaporates or the darker the faster becuase dark colors absorb light and allows a lot of heat to be generated or not at all.
