\(\therefore \,\,a\,\, = \,\,\,\frac{\lambda }{{\sin \,{\theta _1}}}\,\, = \,\,\,\frac{{650\,\, \times \,\,{{10}^{ - 9}}}}{{\sin \,{{30}^ \circ }}}\,\, = \,\,\frac{{650\,\, \times \,{{10}^{ - 9}}}}{{0.5}}\,\,\)
\( = \,\,1.3\,\, \times \,\,{10^{ - 6}}\,\,m\)