A Planar Cross Section Through Two Spherical Waves Emanating from the Sources

Multiple Choice

A planar cross section through two spherical waves emanating from the sources S₁ and S₂ in the plane is shown in the figure. S₁ and S₂ are in phase. The black circles are one and two wavelengths from their respective sources. The lighter circles are one-half and one-and-a-half wavelengths distant from their respective sources. If the waves shown arriving at P₁ both arrive with amplitude A, the resultant amplitude at point P₁ is ​ ​

A) 0.
B) .
C) A.
D) .
E) 2A.