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

Initially number of beats per second = 5∴ Frequency of pipe = 200 ± 5 = 195 Hz or 205 Hz  ...(i) Frequency of second harmonics of the pipe = 2n and number of beats in this case = 10∴ 2n = 420 ± 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