A person hears an echo when shouting near a tall building. Why must the building be at least 17 metres away for a clear echo?
شخص بلند عمارت کے قریب چیخنے پر بازگشت سنتا ہے۔ واضح بازگشت کے لیے عمارت کم از کم17 میٹر دور کیوں ہونی چاہیے؟
Solution & explanation
Using a typical separation time 0.1 s and v ≈ 340 m s⁻¹, sound travels 34 m out and back, so one-way distance is 17 m. The threshold is approximate and varies with the sound and listener.
Independent study answer. Original textbook ↗ · English-medium printed page 60–61.