By minimizing the necessary function we see that the fastest path crosses the surface of the water at the point (35.65, 0). Our brain thinks that the light ray from the target follows the apparent path – the straight line that passes through the points (0, 15) and (35.65).
Looking from above we see the Figure above. Each of our two eyes is looking at the target. The first figure looking from the side helps us analyze what each eye reports to the brain. From above the two apparent paths intersect in a line that passes through the target and is perpendicular to the surface of the water. Thus, the target appears to be directly above its actual position.
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