Question

An organ pipe, open at both ends produce 5 beats per second when vibrated with a source of frequency 200Hz. The second harmonic of the same pipe produces 10 beats per second with a source of frequency 420 Hz. The frequency of source is?

(a) 195Hz

(b) 205Hz

(c) 190Hz

(d) 210Hz

This question was posed to me in examination.

My question is based upon Travelling Waves in division Waves of Engineering Physics I

Answer 1

Correct option is (b) 205Hz

The explanation is: Fundamental frequency of open pipe,

f=200±5=195Hz or 205Hz

Second harmonics of open pipe,

2f=420±10=410Hz or 430Hz

f=205Hz or 215Hz.