Answer:
26 cm
Explanation:
Width of slit = 1.3 mm = d
Wavelength = λ = 420 nm
Distance to screen = 4 m
[tex]x=\frac{\lambda D}{d}\\\Rightarrow x=\frac{420\times 10^{-9}\times 4}{1.3\times 10^{-3}}[/tex]
Width of central maximum is 2 times the distance from the center to first maxima
[tex]2x=2\times \frac{420\times 10^9\times 4}{1.3\times 10^{-3}}=0.00258 m = 2.58\times 10^{-3}\ m =26\ cm[/tex]
Width of the central maximum is 26 cm
