Question

An organ pipe, open from both end produces 5 beats per second when vibrated with a source of frequency 200 Hz. The second harmonic of the same pipes produces 10beats per second with a source of frequency 420 Hz. The fundamental frequency of organ pipe is

• A. 195 HZ
• B. 205 Hz
• C. 190 Hz
• D. 210 Hz

Answer 1

Answer: (B)

205 Hz

Let the fundamental frequency of organ pipe be f

Case 1: $f=200\pm 5=205Hz$ or $195Hz$
Case 2: frequency of 2nd harmonic of organ pipe=2f(as is clear from the second figure)

$2f=420\pm 10orf=210\pm 5$ or $f=205$ or $215$

Hence the fundamental frequency of organ pipe = 205 Hz