In an experiment to determine the velocity of sound in air at room temperature using a resonance tube, the first resonance is observed when the air column has a length of 20.0 cm for a tuning fork of frequency 400 Hz is used. The velocity of the sound at room temperature is 336 ms$-$1. The third resonance is observed when the air column has a length of _____________ cm.
Answer (integer)
104
Solution
<p>$400 = {v \over {4({L_1} + e)}}$ ..... (i)</p>
<p>$400 = {{5v} \over {4({L_2} + e)}}$ ..... (ii)</p>
<p>$\Rightarrow {L_1} + e = {\lambda \over 4} = 21$ cm</p>
<p>${L_2} + e = {{5\lambda } \over 4} = 105$ cm</p>
<p>$\Rightarrow$ e = 1 cm & L<sub>2</sub> = 104 cm</p>
About this question
Subject: Physics · Chapter: Waves · Topic: Wave Motion and Types
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