Identify the fringe or fringes that result from the interference of two waves whose path difference differs by exactly 2λ. Enter the letter(s) indicating the fringe(s) in alphabetical order. For example, if you think that fringes A and C are both correct, enter AC.

The letters indicating the fringes is AD

Explanation:

The waves that differ is:

Δx = 2λ

The equation for phase difference is:

The constructive interference is equal:

ΔΦ = 2nπ

If

n = 0, central bright fringe

n = ±1, first maxima on both fringes

n = ±2, second maxima on both fringes

The conclusion is that ΔΦ = 4π means to A and D bright fringes, so, the answer is AD

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