A source of sound gives 5 beats per second, when sounded with another source of frequency 100 second

Question

A source of sound gives 5 beats per second, when sounded with another source of frequency 100 second $^{-1}$. The second harmonic of the source, together with a source of frequency 205 second $^{-1}$ gives 5 beats per second. What is the frequency of the source?\

Professor PC Thomas Classes · Answer

(a) : Frequency of first source with 5 beats/sec $=100 \mathrm{~Hz}$ and frequency of second source with 5 beats/sec $=205$. The possible frequency of unknown sources $=100 \pm 5=105$ or 95 Hz . Therefore frequency of second harmonic of unknown source $=210 \mathrm{~Hz}$ or 190 Hz .\ As the second harmonic gives 5 beats/second with the sound of frequency 205 Hz , therefore frequency of second harmonic of unknown source should be 210 Hz . The frequency of unknown source $=105 \mathrm{~Hz}$.\