Question

(a) At an air show a jet flies directly toward the stands at a speed of 1200 km/h, emitting a frequency of 3500 Hz, on a day when the speed of sound is 342 m/s. What frequency is received by the observers? (b) What frequency do they receive as the plane flies directly away from them?

Answer 1

a) 1.4 x 10⁵ Hz

b) 1.8 x 10³ Hz

Step-by-step explanation:

a)

`V_(s)` = speed of sound = 342 m/s

`V_(j)` = speed of jet = 1200 km/h = 333.33 m/s

`f_(a)` = actual frequency = 3500 Hz

`f_(obs)` = observed frequency

Observed frequency is given as

`f_(obs) = (f_(s)V_(s))/(V_(s) - V_(f))`

`f_(obs) = ((3500)(342))/(342 - 333.33)\\`

`f_(obs)` = 1.4 x 10⁵ Hz

b)

`V_(s)` = speed of sound = 342 m/s

`V_(j)` = speed of jet = 1200 km/h = 333.33 m/s

`f_(a)` = actual frequency = 3500 Hz

`f_(obs)` = observed frequency

Observed frequency is given as

`f_(obs) = (f_(s)V_(s))/(V_(s) + V_(f))`

`f_(obs) = ((3500)(342))/(342 + 333.33)\\`

`f_(obs)` = 1.8 x 10³ Hz