$y = 4\sin \,\left( {4\pi t - \frac{{\pi x}}{{16}}} \right)$ $(v) = \frac{{{\rm{Co - efficient of}}\,t(\omega )}}{{{\rm{Co - efficient of}}\,x(K)}}$
==> $v = \frac{{4\pi }}{{\pi /16}} = 64\,cm/sec$ along $+x$ direction.
$y_1=5 \sin 2 \pi(75 t-0.25 x)$
$y_2=10 \sin 2 \pi(150 t-0.50 x)$
The intensity ratio $\frac{I_1}{I_2}$ of the two waves is
