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. Let v₂ be the original frequency. |320 - v₂| = 5 ⇒ v₂ = 315 Hz or 325 Hz . Reducing tension decreases frequency. If v₂ = 325 , new v₂’ < 325 , beat = 325 - 320 = 5 or increases, so v₂’ = 313 , beat = 320 - 313 = 7 , consistent. Thus, v₂ = 325 Hz . Using v = fλ and standing-wave condition