Respuesta :
Answer:
192.6 Hz
Explanation:
v = Velocity of sound in air = 335 m/s
Actual frequency = 200 Hz = f
Observed frequency = 208 Hz = [tex]f_o[/tex]
Speed of train = [tex]v_t[/tex]
Doppler effect when the source is moving towards observer
[tex]f_o=\frac{v}{v-v_t}f\\\Rightarrow 208 = \frac{335}{335-v_t} 200 \\\Rightarrow 335-v_t = \frac{335\times 200}{208}\\\Rightarrow 335-v_t=322.11\\\Rightarrow v_t = 12.88\ m/s[/tex]
Doppler effect when the source is moving away from observer
[tex]f_o=\frac{v}{v+v_t}f\\\Rightarrow f_o=\frac{335}{335+12.88}200\\\Rightarrow f_o=192.6\ Hz[/tex]
∴ Frequency he observes as the train moves away is 192.6 Hz
