\({n_f} = \) Frequency of tuning fork \( = 256Hz\)
\(x =\) Beat frequency \(= 5\, bps,\) which is decreasing \((5→2)\) after clanging the tension of piano wire Also, tension of piano wire is increasing so \({n_P} \uparrow \)
Hence \(n_P\uparrow-n_f = x\downarrow\) \(\rightarrow\)Wrong
\(n_f -n_P\uparrow= x\downarrow\) \(\rightarrow\)Correct
\(\Rightarrow\)\(n_P = n_f -x = 256 -5 \,Hz.\)