Learning goal: to understand the assumptions made by the standard two-source interference equations and to be able to use them in a standard problem. for solving two-source interference problems, there exists a standard set of equations that give the conditions for constructive and destructive interference. these equations are usually derived in the context of

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a) which of the following statements explain why the two-source interference equations are not valid for an observer far away from two red led signal lights?

not monochromatic sources
incoherent sources
observed from a distance similar to or smaller than the separation between the sources
a) 1 only
b) 2 only
c) 3 only
d) 1 and 2 only
e) 1 and 3 only
f) 2 and 3 only
g) all three