In Young's double slit experience using monochromatic light of wave length $\lambda$ , the intensity of light at a point on the screen where path different is $\lambda$ is k units. What is the intensity at a point where path different is $\large\frac{\lambda}{3}$

Question

$\begin{array}{1 1} 4k \\ 2k \\\ \large\frac{1}{2}k \\ \large\frac{1}{4}k \end{array}$