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 = (π/2) rad/m . Wavelength: λ = (2π/k) = (2π/(π/2)) = 4 m . Distance between node and antinode: (λ/4) = (4/4) = 1 m . Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields 1 m, illustrating frequency-length-speed interdependence and quantization by boundaries.