A) (256 + 2) Hz
B) (256 - 2) Hz
C) (256 - 5) Hz
D) (256 + 5) Hz
Correct Answer: C
Solution :
Given, frequency \[{{f}_{1}}=256\,Hz\] For tuning fork \[{{f}_{2}}-{{f}_{1}}=\pm 5\], \[{{f}_{2}}=\] frequency of piano \[{{f}_{2}}=(256+5)\,Hz\] or (256 ? 5) Hz When tension is increased, the beat frequency decreases to 2 beats/s. If we assume that the frequency of piano string is 261 Hz, then on increasing tension, frequency, more than 261 Hz. But it is given that beat frequency decreases to 2, therefore 261 is not possible. Hence, 251 Hz i.e, 256 - 5 was the frequency of piano string before increasing tension.
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