Why the frequency in both shallower and deeper part is the same?

1. Mar 28, 2005

ppt

Use water waves as examples.
Put something in the water. When you produce a wave, refraction will occur on above the 'something'.
But why the frequency in both shallower and deeper part is the same?
In addition, the wavelength in the shallower part reduce. Does this means the engery of the wave increase?

Last edited: Mar 28, 2005
2. Mar 28, 2005

Claude Bile

The energy of the photons that comprise the wave is proportional to their frequency. If there were a frequency change at an interface, this would mean energy is being gained or lost at the boundary. Since this is not observed to happen, we conclude that the frequency does not change.

A more quantitative reason is imposed by Maxwell's equations. Maxwell's equations in optical media demand that the electric field be continuous over the boundary for all time. This is only possible if the frequency of the wave does not change.

Claude.