A helium–neon laser (λ = 630 nm) is used in a single-slit experiment with a screen 3.6 m away from the slit. If the slit is 0.10 mm wide, what is the width of the central bright fringe on the screen? Measure this width using the locations where there is destructive interference. in m
1 Answer
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α’ ≈ α
tan α= y/D ≈ sin α’
sinα’ = λm/d (where d is the width of the slit)
y ≈ λmD/d
y ≈ 630*10^-9*1*3.6/0.0001=0.02268 m
So, the width of the central bright fringe
is about 2*y
