In Young's double slit experiment intensity at a point is `((1)/(4))` of the maximum intersity. Angular position of this point is

Explanation

`I = I_("max") cos^(2) ((phi)/(2))`
`:. (I_("max"))/(4) = I_("max") cos^(2) ((phi)/(2))`
`"cos" (phi)/(2) = (1)/(2) "or" (phi)/(2)=(pi)/(3)`
`:. phi =(2 pi)/(3) =((2pi)/(lambda)) Delta x`
Where `Delta x = d sin theta`
`(lambda)/(3) = d sin theta , sin theta = (lambda)/(3d) , theta = sin^(-1) ((lambda)/(3d))`