Two monochromatic coherent sources of wavelength 5000 A are placed along line normal to screen as shown. Then the condition for maxima at the point P is :

Question

$(a)\;y = D \sqrt {\frac{2n \lambda}{d}} \\ (b)\;y=D \sqrt { 2 \bigg(1- \frac{n \lambda}{d} \bigg)} \\ (c)\;y=D \sqrt {1- \frac{n \lambda}{d}} \\ (d)\;None$