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 The unknown frequency is

Options

A. 240 Hz
B. 260 Hz
C. 254 Hz
D. 246 Hz

Answer

C

Explanation

Let `upsilon` be frequency of the unknown source. As it gives 4 beats per second when sounded with a source of frequency 250 Hz,
`therefore upsilon=250pm4=246Hzor254Hz`
Second harmonic of this unknown source = 492 Hz or 508 Hz which gives 5 beats per second, when sounded with a source of frequency 513 Hz.
Therefore unknown frequency, `upsilon=254Hz`.