Equation for a travelling harmonic wave is given as,
$\begin{array}{l}
y(x, t)=2.0 \cos 2 \pi(10 t-0.0080 x+0.35) \\
=2.0 \cos (20 \pi t-0.016 \pi x+0.70 \pi)
\end{array}$
where,
Propagation constant is $\mathrm{k}=0.0160 \mathrm{~m}$
Amplitude is $\mathrm{a}=2 \mathrm{~cm}$
Angular frequency is $\omega=20 \mathrm{~m} \mathrm{rad} / \mathrm{s}$
Phase difference is represented as $\Phi=\mathrm{kx}=2 \pi / \lambda$
(i) For $x=8 \mathrm{~m}=800 \mathrm{~cm}$
$\Phi=0.016 \pi \times 800=12.8 \mathrm{mrad}$
(ii) For $x=1 \mathrm{~m}=100 \mathrm{~cm}$