Calculate the wavelength of light that has its third minimum at an angle of 30.0º when falling on double slits separated by 3.00 µm.


  1. Answer:

    λ = 428.6 nm



    In this case, we must remember that the Young’s double slit experiment is described by the expression

    d sin θ = m λ

    For constructive interference
    , and:

    d sin θ = (m + ½) λ          

    For destructive interference
    , whereas d accounts for the distance between the slits, λ for the wavelength and m for an integer that describes the order of interference
    . Thus, for the given angle 30º, the distance between the slits is 3.00 μm or 3.00 10⁻⁶ m and the order of interference is 3; we therefore use the destructive interference equation  to compute the wavelength as shown below:

    λ = 3×10⁻⁶ sin (30) / (3 +1/2)

    λ = 4.286 10⁻⁷ m

    Or in manometers:

    λ = 428.6 nm

    Best regards.


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