We know that frequency *wavelength = volcity. Or
n*L = v. But frequency n = 500 and v = 360m/s,
Therfore wave length L = v/n = (360)/500 = 0.72 m.
Therefore in a cycle (one full osciilation of ) 360 degree the wave progress 0.72m. The points onthe a wave with aphase difference of 60 degree are at a distance of (60/360)*(0.72m) = 0.12 meter apart.