Physics - Sound Wave Question with Solution | TestHub

Here,
We know beat frequency is the difference of the frequencies of the sources. When unknown source is sounded with known source of frequency 250 Hz, it gives 4 beats/s. It means the frequency of unknown source may be 254 Hz or 246 Hz. Now second harmonic of the source of unknown frequency gives five beats per second, when sounded with a source of frequency 513 Hz. It means the frequency of unknown source may be 518 Hz or 508 Hz. $\text{As }\frac{518}{2}=259\mathrm{Hz}\text{ and }\frac{508}{2}=254\mathrm{Hz}$ Hence unknown frequency is 254 Hz.