A siren mounted on the roof of firehouse emits sound at a frequency of 815 Hz. A steady wind is blowing with a speed of 14.4 m/s. Take the speed of sound in calm air to be 343 m/s (a) Find the wavelength of the sound upwind of the siren. (b) Find the wavelength of the sound downwind of the siren m f he or she is approaching from an upwind (c) Firefighters are approaching the siren from various directions at 19.5 m/s. What frequency does a firefighter hear position, so that he or she is moving in the direction in which the wind is blowing? Hz (d) What frequency does a firefighter hear if he or she is approaching from a downwind position and moving against the wind?

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Xema8 Xema8 · Answer 1 · 2019-09-02T20:29:39+02:00

Answer:

Explanation:

Wind increases the velocity of sound in case of downwind and decreases in case of upwind .

a ) In this case velocity of sound =343 - 14.4 = 328.6

wavelength = velocity / frequency = 328.6/ 815 = 40.32 cm

b ) In this case velocity of sound = 343+14.4 = 357.4

Wavelength = 357.4 / 815 = 43.85 cm

c) In this case apparent frequency = 815 x ( 328.6 + 19.5 )/ 328.6

= 863.36 (sound is moving against the wind )

d ) Apparent frequency =815 x ( 357 + 19.5 ) / 357 ( sound is moving in the direction of wind )

= 859.51