Answer:
134.77 mm
Explanation:
Wave length of light λ = 599 x 10⁻⁹ m
Slit separation d = 20 x 10⁻⁶ m
Screen distance D = 3 m
Distance of second dark fringe from centre
= 1.5 x λ D / d
Putting the values given above
distance = [tex]\frac{1.5\times599\times10^{-9}\times 3}{20\times10^{-6}}[/tex]
= 134.77 x 10⁻³ m
= 134.77 mm.
