A microwave of wavelength \( 2.0 \, \text{cm} \) falls normally on a slit of width \( 4.0 \, \text{cm} \). The angular spread of the central maxima of the diffraction pattern obtained on a screen \( 1.5 \, \text{m} \) away from the slit, will be:
\( 45^\circ \)
\( 60^\circ \)
\( 30^\circ \)
\( 15^\circ \)
