Question

An amplitude modulated (AM) radio wave bends appreciably round the corners of a 1 m × 1 m board but a frequency modulated (FM) wave only bends negligibly. If the average wavelengths of the AM and FM waves are ${\lambda }_a\mathrm{and}{\lambda }_f$,
(a) ${\lambda }_a>{\lambda }_f$
(b) ${\lambda }_a={\lambda }_f$
(c) ${\lambda }_a<{\lambda }_f$
(d) We don't have sufficient information to evaluate the relation of ${\lambda }_a\mathrm{and}{\lambda }_f$.

Answer 1

(a) ${\lambda }_a>{\lambda }_f$

An electromagnetic wave bends round the corners of an obstacle if the size of the obstacle is comparable to the wavelength of the wave. An AM wave has less frequency than an FM wave. So, an AM wave has a higher wavelength than an FM wave and it bends round the corners of a 1 m $\times$ 1m board.
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