Plane wave of `lamda=600` nm incident normally on a slit of width 0.18 mm. Calculate the total angular wideth of the central maximum.

Explanation

Data supplied
`n=1,a=0.18xx10^(-3)m, lamda=600xx10^(-9)m`
`a sin theta =nlamda` Since `theta` is a very small `sin theta ~~ theta`
`:. theta=(n lamda)/a=(1xx600xx10^(-9))/(0.18xx10^(-3))=3.33xx10^(-3)`radian
`:.`Total angular width `=2 theta=6.66xx10^(-3)` radian