Waves - Result Question 53

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55. A source of unknown frequency gives 4 beats/s, when sounded with a source of known frequency $250 Hz$. The second harmonic of the source of unknown frequency gives five beats per second, when sounded with a source of frequency $513 Hz$. The unknown frequency is

======= ####55. A source of unknown frequency gives 4 beats/s, when sounded with a source of known frequency $250 Hz$. The second harmonic of the source of unknown frequency gives five beats per second, when sounded with a source of frequency $513 Hz$. The unknown frequency is

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/waves/waves—result-question-53.md (a) $246 Hz$

(b) $240 Hz$

(c) $260 Hz$

(d) $254 Hz$

[2013]

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Answer:

Correct Answer: 55. (d)

Solution:

  1. (d) When sounded with a source of known frequency fundamental frequency

$=250 \pm 4 Hz=254 Hz$ or $246 Hz$

$2^{\text{nd }}$ harmonic if unknown frequency (suppose) $254 Hz=2 \times 254=508 Hz$

As it gives 5 beats

$\therefore 508+5=513 Hz$

Hence, unknown frequency is $254 Hz$