A glass of water appears clear, but a swimming pool appears blue. At some point there must be a switch and I am wondering if anyone knows what that point is (or if its so gradual we can't tell). Does the switch occur because light has traveled further through the swimming pool than in the glass of water and is thus scattered more and more red light is absorbed to excite vibrational levels?

  • $\begingroup$ Physically it is gradual. Perception wise, there is a switch. $\endgroup$ – Paul Childs Jul 24 '19 at 4:30

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