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STD 11 - 14. waves and sound — NEET STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceNEETSTD 11 - 14. waves and sound4 Marks
Question
A source of frequency $\nu$ gives $5$ beats/second when sounded with a source of frequency $200 \;Hz$. The second harmonic of frequency $2\nu$ of source gives $10$ beats/second when sounded with a source of frequency $420\; Hz$. The value of $v$ is .... $Hz$
✓

Answer

(b) Initially number of beats per second $= 5$

$ \therefore$ Frequency of pipe $= 200 \pm \,5 = 195 Hz$ or $205 Hz$ ...$(i)$

Frequency of second harmonics of the pipe $= 2n$ 

and number of beats in this case $= 10$

$ \therefore$ $2n = 420 \pm \, 10 $

==> $410 Hz$ or $430 Hz$

==> $n = 205 Hz$ or $215 Hz$ ... $(ii)$

From equation $(i)$ and $(ii)$ it is clear that $n = 205 Hz$

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