Problem 4.151

A plane harmonic wave with frequency \(\omega\) propagates at a velocity \(v\) in a direction forming angles \(\alpha, \beta, \gamma\) with the \(x, y, z\) axes. Find the phase difference between the oscillations at the points of medium with coordinates \(x_{1}, y_{1}, z_{1}\) and \(x_{2}, y_{2}, z_{2}\)