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    Destructive interference

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    A mixture of red light (vacuum = 661 nm) and green light (vacuum = 551 nm) shines perpendicularly on a soap film (n = 1.41) that has air on either side. What is the minimum nonzero thickness of the film, so that destructive interference causes it to look red in reflected light?
    answer in nanometers

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    Solution Preview

    n= 1.41
    lambda red= 661 nm
    lambda green= 551 nm

    For maximum intensity, 2dn=(m+1/2)lambda --- Eq (1)
    For minimum intensity, 2dn=(m)lambda --- Eq (2)

    The term 1/2 is introduced to take into account the phase change on ...

    Solution Summary

    The solution calculates thickness of a soap film using the concept of destructive interference