If a message signal of frequency \('f_m'\) is amplitude modulated with a carrier signal of frequency \('fc'\) and radiated through an antenna, the wavelength of the corresponding signal in air is :
(1) \(\frac{c}{f_c-f_m}\)
(2) \(\frac c{f_m}\)
(3) \(\frac{c}{f_c+f_m}\)
(4) \(\frac{c}{f_c}\)