Physics - Sound Wave Question with Solution | TestHub

Key Idea The number of beats will be the difference of frequencies of the two strings. Frequency of first string $f_1=\frac{1}{2l_1}\sqrt{\frac{T}{m}}$ $$\begin{array}{rl}& =\frac{1}{2\times 51.6\times 10^{-2}}\sqrt{\frac{20}{10^{-3}}}\\ & =137.03\mathrm{Hz}\end{array}$$ Similarly, frequency of second string $$\begin{array}{rl}& =\frac{1}{2\times 49.1\times 10^{-2}}\sqrt{\frac{20}{10^{-3}}}\\ & =144.01\end{array}$$ Number of beats $={\mathrm{f}}_2-{\mathrm{f}}_1=144-137$ $=7$ beats