Given,
The fundamental frequency of the bell, f=880 Hz
The speed of the bell, v₀=3.5 m/s
The speed of the sound, v=343 m/s
The pitch heard by the observer due to the doppler shift is given by,
[tex]f_0=\frac{f}{1-\frac{v_0}{v}}[/tex]On substituting the known values,
[tex]\begin{gathered} f_0=\frac{880}{1-\frac{3.5}{343}} \\ \approx889\text{ Hz} \end{gathered}[/tex]Thus the frequency heard by the observer is 889 Hz.
Therefore the correct answer is option 2.
