Answer:
.09 mm
Explanation:
In case of diffraction by single slit with width a the width of central maxima is given below
width = 2 λD/a
where λ is wavelength of light , D is distance of screen , a is width o slit
substituting the given values
14 x 10⁻³ = [tex]\frac{2\times530\times10^{-9}\times1.2}{a}[/tex]
a = .09 mm
b) If a is greater , width of central maxima will be less wide.