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Question
Monochromatic light of wavelength 4300 Å falls on a slit of width ‘a’. For what value of ‘a’ the first maximum falls at 30° ?
Solution
`λ = 4300 Å `
`= 4300 xx10^-10 m`
a = ?
n = 1
`sin θ = L/a `
`therefore a = λ / sin 30 = (4300xx10 ^-10)/(1/2)`
`a= 4300xx10^-10xx2`
`= 8600 xx10^-10 m`
for first maximum
`sin θ = (n+1/2)λ/a`
`= 3/2 xx (4300xx10^-10)/(1/2)= 1.29 µ"m"`
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