Understanding E/M Waves and Frequency Changes in Different Mediums

[dervast]

Hi i know when i electromagnietic wave changes medium (for example it goes from air to the water) the waveklength don't cchange but the frequency.. How is this explained? Thx a lot

 

[Dr.Brain]

Its actually the other way. When EM wave enters from one medium to another . its wavelength decreases but frequency remains the same.

 

[jtbell]

And the reason why the frequency has to be the same is that the electric and magnetic fields have to be continuous functions of position. That is, the "ends" of the waves on the two sides of the boundary have to match up. If the frequency were different in the two media, this wouldn't be true most of the time.