# For the travelling harmonic wave y(x,t) = 2cos2π(10t-0.008x + 0.35) where x and y are in cm and t is in s. The phase difference between oscillatory motion of two points separated by a distance of 0.5 m is ?

For a wave motion, phase difference $\delta \phi$ and path difference $\delta x$ are related as ,
$\delta \phi = \frac{2 \pi}{\lambda} \delta x = k \delta x$
Comparing the given equation with, $y = a \cos \left(\omega t - k x\right)$ we get,
$k = 2 \pi \cdot 0.008$
so,$\delta \phi = k \cdot 0.5 \cdot 100 = 2 \pi \cdot 0.008 \cdot 0.5 \cdot 100 = 2.5 r a d$