Q. 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
A) 254 Hz
B) 246 Hz
C) 240 Hz
D) 260 Hz
Explanation
[Solution from source] 4 beats with 250 Hz means f = 254 Hz or 246 Hz. Second harmonics are 508 Hz or 492 Hz; only 508 Hz gives 513 − 508 = 5 beats per second. So f = 254 Hz; 246 Hz would give 21 beats. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.