# 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 frequenc 513 Hz. The unknown frequency is: Option 1) 260 Hz Option 2) 254 Hz Option 3) 246 Hz Option 4) 240 Hz

As discussed in @7263

when sounded with a source of known frequency, fundamental frequency

Second harmonic of unknown frerquency (suppose)

254 Hz = 2 x 254 = 508 Hz

508 + 5 = 513 Hz

Hence, unknown frequency is 254 Hz.

Option 1)

260 Hz

This option is incorrect

Option 2)

254 Hz

This option is correct

Option 3)

246 Hz

This option is incorrect

Option 4)

240 Hz

This option is incorrect

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