Question

A narrow sound pulse (for example, a short pip by a whistle) is sent across a medium. (a) Does the pulse have a definite (i) frequency, (ii) wavelength, (iii) speed of propagation? (b) If the pulse rate is 1 after every 20 s, (that is the whistle is blown for a split of second after every 20 s), is the frequency of the note produced by the whistle equal to 1/20 or 0.05 Hz ?

Answer 1

a)

A narrow sound pulse (a short pip by a whistle) has neither a definite wavelength nor a definite frequency. But, it has a definite speed of propagation equal to the speed of sound.

Thus, a narrow sound pulse has a definite speed of propagation only.

b)

The frequency of the note produced by the whistle is not equal to 1 20 or 0.05 Hz. This value gives the frequency of repetition of the pip of whistle.