Question

If two waves of same frequency and same amplitude respectively on superimposition produced a resultant disturbance of the same amplitude the wave differ in phase by

• A. $\pi$
• B. $2\pi/3$
• C. $\pi/2$
• D. Zero

Answer 1

Answer: (B)

$2\pi/3$

Answer 2

$A = \sqrt{{A_{1}}^{2} + {A_{2}}^{2} + 2A_{1}A_{2}\cos\varphi}$

A² = A² + A² + 2A² cos $\varphi$ [A₁ = A₂ = A given]

cos φ = – 1/2 ⇒ $\varphi = 120{^\circ} = \frac{2\pi}{3}$