As shown in the figure below, a source at S is sending out a spherical wave:
E_{1}=(A×D/r) cos(wt-2πr/λ); where r is the distance to source S. In addition, there is another plane wave propagating along x axis: E_{2}=Acos(wt-2πx/λ).
These two waves both projected on a vertical screen as shown in the figure. Please calculate the intensity I along y axis (I should be a function of y, the distance from x axis). D is the distance between the screen and the source.
Hint: For a wave E=E_{0}cost (wt + q), I = ^{2} = E_{0}^{2}. Also r = .
For k<<1, » 1+k^{2}/2. cosA+cosB = 2cos[(A+B)/2] cos[(A-B)/2]