\(n\) મી અપ્રકાશિત શલાકા માટે, \({x_n} = \,\,\frac{{nD\,\lambda }}{d}\)
\({x_3} = \,\,\frac{{3\,\, \times \,\,100\,\, \times \,\,6\,\, \times \,\,{{10}^{ - 7}}}}{{0.012}}\,\,\, = \,\,\,1.5\,\, \times \,\,{10^{ - 2}}\,\,m\,\,\, = \,\,1.5\,\,\,cm\)
\(\,\,[\,\because \,\,n\,\, = \,\,3]\)