In a single slit diffraction experiment first minimum for red light (660 nm) 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=nλSo for first minima of red  sinθ=1×λRdand as first maxima is midway between first and second minima, for wavelength λ'its position will be dsinθ'=λ'+2λ'2⇒sinθ'=3λ'2dAccording to given condition sinθ=sinθ'⇒λ'=23λR so λ'=23×6600=440 nm =4400 Ao