Q.
In a single slit diffraction experiment, first minimum for red light (660nm) coincides with first maximum of some other wavelength λ′. The value of λ′ is
In a single slit diffraction experiment, position of minima is given by dsinθ=nλ .
So, for first minima of red, sinθ=1×(dλR​​) .
And as first maxima is midway between first and second minima, for wavelength λ′, its position will be dsinθ′=2λ′+2λ′​⇒sinθ′=2d3λ′​.
According to given condition sinθ=sinθ′ ⇒λ′=32​λR​
So, λ′=32​×6600=440nm=4400A˚ .