For a travelling harmonic wave y(x, t)=2.0 cos 2 π(10 t-0.0080 x+0.35), where x and y are in cm and t in s. The phase difference between oscillatory…

For a travelling harmonic wave $\displaystyle y(x, t)=2.0 \cos 2 \pi(10 t-0.0080 x+0.35)$, where x and y are in cm and t in s. The phase difference between oscillatory motion of two points separated by a distance of $\displaystyle 0.5 \mathrm{~m}$ is :