Wednesday 1 October 2014

electromagnetism - Why does frequency remain unchanged in light refraction but wavelength doesn't?



Since the frequency of an electromagnetic wave does not change during refraction but the velocity changes, the wavelength must therefore change. But why doesn't the frequency change in the first place? I heard answers like that frequency is the property of the source but wavelength is not. Even of this is the right answer explanations are not adequate.



Answer



Here's a qualitative argument. A wave propagates in space and time, but the boundary is a barrier in space rather than a barrier in time. Hence the spatial part of the propagation will change, but the time part will not.


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