Answer: 0.757m; 0.881m; 432.70Hz; 371.89Hz
Explanation:
Give the following :
Velocity of train (Vt) = 26m/s
Frequency of sound (Fs) = 420Hz
Speed of sound (Vs) = 344m/s
1) wavelength = (Vs - Vt) / Fs
Wavelength = (344 - 26) / 420 = 318/420 = 0.757m
11) Wavelength = (Vs + Vt) / Fs
Wavelength = (344 + 26) / 420 = 370/420 = 0.881m
111) According to the doppler effect :
Fl = [(V + Vl) / (V + Vs)] * fs
Fl = frequency of listener ; fs = frequency of sound source ; V = speed of sound ; Vl = Velocity of listener ; Vs = speed of sound source
Vs = - ve (train moving towards listener)
Fl = [(V + Vl) / (V + Vs)] * fs
Fl = [(344 + 0) / (344 - 26)] * 400
Fl = (344 / 318) * 400 = 432.70Hz
1V) Vs = + ve (train moving away listener)
Fl = [(V + Vl) / (V + Vs)] * fs
Fl = [(344 + 0) / (344 + 26)] * 400
Fl = (344 / 370) * 400 = 371.89Hz
