Two sinusoidal waves of equal frequency and equal amplitude A travel in the same direction. Their phase difference is 120°. What is the amplitude Aᵣₑₛ of the resultant wave formed by superposition?
Options

Question

Two sinusoidal waves of equal frequency and equal amplitude A travel in the same direction. Their phase difference is 120°. What is the amplitude Aᵣₑₛ of the resultant wave formed by superposition?

Options

G1 Physics · Accepted Answer

The resultant amplitude of two waves is Aᵣₑₛ = √[A₁²+A₂²+2A₁A₂ cosφ]. Here, A₁ = A₂ = A, φ = 120°. Thus, Aᵣₑₛ = √[2A²+2A² cos120°]. Since cos120° = −1/2, Aᵣₑₛ = √(2A²−A²) = A. Correct option: B.