1. The problem statement, all variables and given/known data The diagram attached shows two coherent sources P and Q which produce waves of the same phase with wavelength , labda . If the two waves meet at the point R , the phase difference between waves at R is ?? 2. Relevant equations y=a sin (omega t + kx) 3. The attempt at a solution i have problems obtaining the equation for wave p and q respectively , i know i have to find the superposition of the wave ?