In figure, parallel beam of light is incident on the plane of the slits of a Young's double-slit experiment. Light incident on the slit `S_(1)` passes through a medium of variable refractive index `mu = 1 + ax` (where 'x' is the distance from the plane of slits as shown), up to distance 'I' before falling on `S_(1)`. Rest of the space is filled with air. If at 'O' a minima is formed. then the minimum value of the positive constant a (in terms of l and wavelength `lambda` in air) is

Options

A. `(lambda)/(l)`
B. `(lambda)/(l^(2))`
C. `(l^(2))/(lambda)`
D. None of these

Answer

B