In a single slit diffraction expriment, first minimum for red light `(660 nm)` coincide with first maximum of some other wavelength `lambda'`. Calculate `lambda'`.

Explanation

For minima, `d sin theta=n lambda`
`n=1,d*((y_(1))/(D))=1.(6600Å)`
`y_(1)=(D)/(d)*(6600Å)`
Now, first maximum is approximately between the first minima and second minima.
`yI=((y_(1)+y_(2))/(2))=((1+2)/(2))*(Dlambda)/(d)`
As `y_(1)=y_(1)implies(D)/(d)(6600Å)=((3)/(2))(D)/(d)lambda`
`lambda.=(2xx6600Å)/(3)=4400Å`