- #1
fluidistic
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Starting from Fermat's principle, one can reach Snell's law. In the derivation, one find that there can be a critical angle at which light doesn't pass anymore from a material to another. That is, if you consider 2 materials and the light starts in the material of greater refractive index.
For example if we have air and water. Water has a greater refractive index than air, mathematically we have [tex]n_{\text{water}}>n_{\text{air}}[/tex].
However there is no critical angle if we are in the air and throw a light beam to the water. It means that any light beams heading into the water will cross the water surface and eventually be under water' surface. Then why can we see a reflexion over water surface? It may be our own face, Sun or clouds, but there is a reflexion of light over water. How is that possible?
For example if we have air and water. Water has a greater refractive index than air, mathematically we have [tex]n_{\text{water}}>n_{\text{air}}[/tex].
However there is no critical angle if we are in the air and throw a light beam to the water. It means that any light beams heading into the water will cross the water surface and eventually be under water' surface. Then why can we see a reflexion over water surface? It may be our own face, Sun or clouds, but there is a reflexion of light over water. How is that possible?