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. |300 - v₂| = 6 ⇒ v₂ = 294 Hz or 306 Hz . Decreasing tension decreases frequency. If v₂ = 306 , new v₂’ < 306 , beat = 306 - 300 = 6 or decreases, so v₂’ = 296 , beat = 300 - 296 = 4 , consistent. Thus, v₂ = 306 Hz . Using v = fλ and standing-wave condition