Question

8. A sound wave propagates in air at 27°C with frequency 4.00 kHz. It passes through a region where the temperature gradually changes and then moves through air at 0°C. Give numerical answers to the fol- lowing questions to the extent possible and state your reasoning about what happens to the wave physically. (a) What happens to the speed of the wave? (b) What happens to its frequency? (c) What happens to its wavelength? Figure P17.7

Answer 1

The speed gradually change form v = (331 m/s) (1 + 27 degree C/273)^1/2 = 347 m/s v = (331 m/s) [1 + 0 degree c/273 degree c]^1/2 = 331 m/s. a 4.6 % decrease. The cooler air at the same pressure is mole dense The frequency is unchanged because every wave test in the hot air becomes one west without delay in cold air. The wavelength decreases by 4.6 % from v/f = 347/4000 = 86.7 mm v/f = (331)/000 = 82.8 mm The tests are mole clouded together when they more mole slowly.