Practice question

**Beat formation** is interference in time with time-varying amplitude. Frequencies close together generate slow modulation, count in given duration obtained by multiplying beat frequency by duration, e.g., 6 Hz × 5 s = 30 beats. Form: y = A sin (kx) cos (ω t) , k = 2π rad/m . Wavelength: λ = (2π/k) = (2π/2π) = 1 m . Distance between nodes: (λ/2) = (1/2) = 0.5 m . Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields 0.5 m, illustrating frequency-length-speed interdependence and quantization by boundaries.