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° ?

Answer 1

`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"`