A slit is illuminated by red light of wavelength 6500 A0 . The first minimum is obtained atθ=300 . The width of the slit is

Wavelength λ=6500 A0=6500×10−10 m Angular fringe width θ=300 Width of the slit a=?          a=λθ ⇒  a=6500×10−10(π6) ⇒  a=1.24×10−6m ⇒  a=1.24 micron