Derive the minimum distance of the obstacle from the source in order to hear a distinct echo. [3 MARKS]
Derive the minimum distance of the obstacle from the source in order to hear a distinct echo. [3 MARKS]
Time interval for distinct sound : 1 Mark
Calculation : 1 Mark
Result : 1 Mark
To hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1 s.
If we take the speed of sound to be 344 ms−1 at a given temperature, say at 22 ∘C in air, the sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1 s.Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least 344×0.1=34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance, that is, 17.2 m.
Time interval for distinct sound : 1 Mark
Calculation : 1 Mark
Result : 1 Mark
To hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1 s.
If we take the speed of sound to be 344 ms−1 at a given temperature, say at 22 ∘C in air, the sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1 s.Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least 344×0.1=34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance, that is, 17.2 m.
