question_answer

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

Correct Answer: A

Solution :

 Here,      Hence, unknown frequency is 254 Hz.