In Young's double slit experiment slit separation d=5λ. Then angular separation between 5th bright fringe and 2nd dark fringe (in radian) is

Distance of 5th bright fringe from the centre of screen, y5=5λD/d and the distance of second dark fringe from the centre of the screen y2=1+d2λD/d=3λD2d∴ Angular separation =y5−y2D=5λDd−3λD2dD=7λ2d=7λ2×5λ=0.7 radian