A plane electromagnetic wave that is a superposition of two independent orthogonal plane waves and can be written as the real part of E = E exp [i(kz-wot)] + y E exp [i(kz - wot+n)] where k, co, E, and E are real If the plane wave is split and recombined on a screen after the two portions, which are polarized in the x- and y- directions, have traveled an optical path difference of 27/k, the observed average intensity will be proportional to (a) E+ E (b) E-E (c) (E+ E) (d) (E-E)