A plane harmonic wave with frequency ω\omegaω propagates at a velocity vvv in a direction forming angles α,β,γ\alpha, \beta, \gammaα,β,γ with the x,y,zx, y, zx,y,z axes. Find the phase difference between the oscillations at the points of medium with coordinates x1,y1,z1x_{1}, y_{1}, z_{1}x1,y1,z1 and x2,y2,z2x_{2}, y_{2}, z_{2}x2,y2,z2