1. The problem statement, all variables and given/known data A wave travels along a straight line with speed 1m/s . The initial phase angle is 0. Wavelength = 4m. Measured from initiation of waves, when will the phase of the point 5m from the wave source first be 180°? 3. The attempt at a solution Phase difference = (2π/λ) path difference π = (2π/λ) 5. But I really have no idea what I'm doing here. The LHS and RHS are not equal. What's this??