Practice question

**Wave addition** governed by phase difference determines resultant intensity ∝ A². Phase arises from path difference Δ = (2π/λ)·Δx, and resultant formula captures interference condition quantitatively for NCERT problems. Amplitude: A = 2a cos (Φ/2) , a = 4 m , Φ = (π/3) . A = 2 × 4 cos (π/6) = 8 × (√(3)/2) ≈ 6.93 m . Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields 6.9 m, illustrating frequency-length-speed interdependence and quantization by boundaries.