A tuning fork of frequency $100\text{ Hz}$ when sound together with another tuning fork of unknown frequency…

A tuning fork of frequency $100\text{ Hz}$ when sound together with another tuning fork of unknown frequency produces 2 beats per second. On loading the tuning fork whose frequency is not known and sounded together with the same tuning fork produces one beat, then the frequency of the unknown tuning fork (in Hz) is
  1. 102
  2. 98
  3. 99
  4. 101

Solution

Unknown frequency may be $102\text{ Hz}$ or $98\text{ Hz}$. On loading this tuning fork, its frequency will decrease. Suppose they become $101\text{ Hz}$ or $97\text{ Hz}$. With $100\text{ Hz}$, beat frequency will be $1\text{ Hz}$ or $3\text{ Hz}$. Given frequency is $1\text{ Hz}$. Hence, unknown frequency should be $102\text{ Hz}$.

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