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14.Waves and Sound
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Three similar wires of frequency $n_1, n_2$ and $n_3$ are joined to make one wire. Its frequency will be
A
$n = {n_1} + {n_2} + {n_3}$
B
$\frac{1}{n} = \frac{1}{{{n_1}}} + \frac{1}{{{n_2}}} + \frac{1}{{{n_3}}}$
C
$n = n _{1} \times n _{2} \times n _{3}$
D
$n =\frac{ n _{1}+ n _{2}+ n _{3}}{3}$
(AIPMT-2000)
Solution
(b) $n = \frac{1}{{2l}}\sqrt {\frac{T}{m}} $
==> ${n_1}{l_1} = {n_2}{l_2} = {n_3}{l_3} = k$
${l_1} + {l_2} + {l_3} = l$
==>$\frac{k}{{{n_1}}} + \frac{k}{{{n_2}}} + \frac{k}{{{n_3}}} = \frac{k}{n}$
==> $\frac{1}{n} = \frac{1}{{{n_1}}} + \frac{1}{{{n_2}}} + \frac{1}{{{n_3}}} + ……..$
Standard 11
Physics
