d$()=($n$-)$ from this formul now answer this question $2.$ Red light at wavelength of $720.$ nm is directed a double slit of separation $0\mathrm{.}13$ mm and an interference pattern is created on a screen $2\mathrm{.}5$ m away. How far from the central bright fringe is $($a$)$ the $2$nd nodal line and