In a diffraction pattern due to a single slit
of width 'a', the first minimum is observed at
an angle 30° when light of wavelength 5000 Å is
incident on the slit. The first secondary maximum
is observed at an angle of :
(1) ``sin^{-1}(\frac 14)``
(2) ``sin^{-1}(\frac 23)``
(3)``sin^{-1}(\frac 12)``
(4) ``sin^{-1}(\frac 34)``