Answer:
Y = 3.87 x 10⁻³ m = 3.87 mm
Step-by-step explanation:
This problem can be solved by using Young's double-slit experiment formula:

where,
Y = fringe spacing = ?
L = slit to screen distance = 2 m
λ = wavelength of light = 580 nm = 5.8 x 10⁻⁷ m
d = slit width = 0.3 mm = 3 x 10⁻⁴ m
Therefore,

Y = 3.87 x 10⁻³ m = 3.87 mm