Why Does Light Appear to Bend in Water
Why Does Light Appear to Bend in Water — Before this bending I think again about our eyes. We firmly trust the words "I saw it clearly with my own eyes." But the submerged stick teaches: the eye only followed the light honestly and cannot know where that light was bent on the way. What we saw is not the thing, but light that set out from it and arrived through several media. Then is it not the same when we look at a person? Perhaps we did not see them, but light that passed through them and through years, rumor, and our own heart. To know that the seen position may not be the true position — that is where humility begins.
A stick in a clear stream looks broken at the surface, and a coin underwater seems to float higher than it is. Reach in, and the stick is whole, the coin deeper than it appeared. Our eyes are surely seeing something wrong. But if we are fooled the same way every time, it is not illusion — it is some law.
The first to measure this discrepancy in earnest was Ptolemy of ancient Alexandria, who tabulated the angles at which light bends entering water. But the exact rule binding those angles eluded humanity for over a thousand years. The Arab Ibn Sahl and Persian scholars drew near, and in the seventeenth century the Dutchman Snell and the Frenchman Descartes at last wrote the rule as a formula. The bending we see daily yet could not explain took mankind fifteen centuries to capture in an equation.
Here is the heart of it: light travels at different speeds in different media — slower in water than air, slower still in glass. When light enters another medium at a slant, one edge slows first and the direction of travel bends. It is like a marching column entering mud at an angle: one foot sinks first, and the line curves. So the light from a submerged stick bends at the surface as it reaches our eyes, and the brain, trusting that light came straight, misplaces the stick. The stick is not bent — the light that drew it is bent. Our eyes only followed the light honestly.
- Glasses and magnifiers tame this bending to sharpen a blurred world. Adding a magnifier to aging eyes bends light just so, to form the image on the retina.
- Optical fiber traps light inside a thread of glass and sends it far. Because the light keeps bending back inward at the edges, a single strand of glass becomes a cable joining continents.
- When an angler aims at a fish, taking a touch below where it appears is the old wisdom of experience — for refraction makes the fish seem to float higher than it is.
映, 무언가가 비쳐 보인다는 것은 빛이 매질을 거치며 꺾여 우리 눈에 닿은 결과다.
Meet this hanja in Cheonjamun →Before this bending I think again about our eyes. We firmly trust the words "I saw it clearly with my own eyes." But the submerged stick teaches: the eye only followed the light honestly and cannot know where that light was bent on the way. What we saw is not the thing, but light that set out from it and arrived through several media. Then is it not the same when we look at a person? Perhaps we did not see them, but light that passed through them and through years, rumor, and our own heart. To know that the seen position may not be the true position — that is where humility begins.
