Answer:
Fringe width = 21 mm
Explanation:
Fringe width is given by the formula
[tex]\beta = \frac{\Lambda L}{d}[/tex]
here we know that
[tex]\Lambda = 564 nm[/tex]
L = 4.0 m
d = 0.108 mm
now from above formula we will have
[tex]\beta = \frac{(564 \times 10^{-9})(4.0 m)}{0.108\times 10^{-3}}[/tex]
[tex]\beta = 0.021 meter[/tex]
so fringe width on the wall will be 21 mm