d
અપ્રકાશિત શલાકા માટે \(x\,\, = \,\,\left( {2n\,\, - \,\,1} \right)\,\,\frac{{\lambda D}}{{2d}}\,\,\therefore \,\,\lambda \,\, = \,\,\frac{{2xd}}{{\left( {2n\,\, - \,\,1} \right)D}}\)

\( = \,\,\frac{{2\,\, \times \,{{10}^{ - 3}}\,\, \times \,\,\left( {0.9\,\, \times \,\,{{10}^{ - 3}}} \right)}}{{\left( {2\,\, \times \,2\,\, - \,\,1} \right)\,\, \times \,\,1}}\,\,\,0.6\,\, \times \,\,{10^{ - 6}}\,\,m\,\, = \,\,6\,\, \times \,\,{10^{ - 5}}\,\,cm\)