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. Beat frequency: vbₑₐt = 495 - 490 = 5 Hz . Beats in 8 s: 5 × 8 = 40 . Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields 40, illustrating frequency-length-speed interdependence and quantization by boundaries.