Two coherent waves have equal individual intensity I₀ and phase difference 120°. If their resultant intensity is NI₀, find N.

Question

G1 Physics · Accepted Answer

For equal intensities, I = 4I₀ cos²(φ/2). Here, φ = 120°, so φ/2 = 60°. Thus, I = 4I₀ cos²60° = 4I₀(1/2)² = I₀. Therefore, N = 1.