[list][*]When the wavelength [i]λ[/i] increases but the distance between slits [i]d[/i] stays the same, the angle [i]θ[/i] for bright fringes increases and the interference pattern spreads out. [/*][*]Increasing the slit spacing [i]d[/i] reduces [i]θ[/i], so the interference patterns are closer together. [/*][*]The effect of the slit width [i]b[/i] is that the single slit diffraction pattern modulates the [i]N[/i]-slit pattern. In other words, the single slit curve becomes the envelope of the [i]N[/i]-slit curve, i.e. the [i]N[/i]-slit curve is pushed under the single-slit curve.[/*][*]As the number of slits [i]N[/i] increases, the primary maxima are observed at the same angles, but get narrower and brighter. In addition to that, ([i]N-2)[/i] secondary maxima appear.[/*][/list]