UP Th urns 8hlae Km distant ose frequency is n of this rone is t a speed of 1.33

Question

UP Th urns 8hlae Km distant ose frequency is n of this rone is t a speed of 1.33 m 72. A cat ca send an 120,00 length Ysis) the same rom greatest )frequency 73. A ba the e the e 74. A ny as s 62. The siren of a fire engine is heard in three 75. when the fire engine is traveling (a) towr at 30 km/h, (b) toward the listener at 50 km/h, and e listener 76. (c) away from the listen er at 20 km/h. Rank th heard, from highest to lowest. e pitches three shock waves are produced by supersonic air craft. Rank their speeds from fastest to slowest, ve eet pairs peak BC

Explanation / Answer

According to Doppler's effect -

When the source is approaching towards the lisner, the apparant frequency is given by -

f" = f*[ c / (c - v)]

where c is the velocity of sound and v is the velocity of the source.

And when the source is moving away from the lisner, the apparent frequency is given by -

f" = f*[ c / (c + v)]

So, when the engine's speed is 50 km/h, the pitch heard shall be the highest.

Second rank of the pitch, when the engine's speed is 30 km/h toward's the lisner.

And the lowest pitch, when the engine speed is 20 km/h away from the lisner.

So, the rank is -

(b) > (a) > (c)

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