# Doppler effect and different frames

The equation of a travelling sine wave is given by $$y=Asin(wt-kx)$$ On seeing this from a different reference frame,we use galilean transformation,where,in new frame,replacing x by x-vt,the new equation is, $$y=Asin(w't-kx)$$ Where$$w'=w+kv$$ So,the frequency gets changed,not wavelength.

• But DOPPLER EFFECT says that for a moving observer wavelength of the wave changes.Where lies the problem?