Practice question

**Interference of waves** produces enhancement or cancellation based on phase. Two equal amplitude waves out of phase by π cancel completely, A = 0, while in-phase superposition doubles amplitude to 2a, demonstrating energy redistribution without violation of conservation. Beats require two waves with slightly different frequencies to produce periodic interference, resulting in amplitude modulation. Equal amplitudes or specific wavelengths are not necessary. Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields Slightly different frequencies, illustrating frequency-length-speed interdependence and quantization by boundaries.