Question

Consider the interference pattern from the three slits illustrated (shown in figure). Assume the openings of the individual slits are the same (≤ λ/2) . At what value of θ is the first principal maximum? (i.e., the wavelets from all three slits are in phase).

Answer 1

The electric field E(θ) on the screen is the sum of the fields produced by the slits individually:

The expression for I (θ ) shows that the first principal maximum occurs at δ = 2π , i.e.,