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14.Waves and Sound
medium
If ${n_1},{n_2},{n_3}.........$ are the frequencies of segments of a stretched string, the frequency $n$ of the string is given by
A
$n = {n_1} + {n_2} + {n_3} + .......$
B
$n = \sqrt {{n_1} \times {n_2} \times {n_3} \times .......} $
C
$\frac{1}{n} = \frac{1}{{{n_1}}} + \frac{1}{{{n_2}}} + \frac{1}{{{n_3}}} + .....$
D
None of these
Solution
(c) For a vibrating string
${n_1}{l_1} = {n_2}{l_2} = {n_3}{l_3}….. = $constant $= k$ (say) $= nl$
Also ${l_1} + {l_2} + {l_3} + {l_4} + …… = 1$
$\frac{k}{{{n_1}}} + \frac{k}{{{n_2}}} + \frac{k}{{{n_3}}} + \frac{k}{{{n_4}}} + …. = \frac{k}{n}$==> $\frac{1}{n} = \frac{1}{{{n_1}}} + \frac{1}{{{n_2}}} + \frac{1}{{{n_3}}} + …….$
Standard 11
Physics