A monochromatic light of wavelength $6000 \mathrm {~\AA}$ is incident on the single slit of width 0.01 mm. If the diffraction pattern is formed at the focus of the convex lens of focal length 20 cm, the linear width of the central maximum is:\\
(1) 60 mm\\
(2) 24 mm\\
(3) 120 mm\\
(4) 12 mm