Ok here's the problem: Waves are produced by two point sources S and S' vibrating in phase. SEe the accompanying diagram. X is apoint on the second nodal line. The path difference SX - S'X is 4.5cm The wavelength of the waves is approxiately______. ````` o X ``````| ``````| ``````| So------ o S' I know what the answer is, but I really don't understand where this second nodal line would occur.