Wave Motion 2 Question 1

1. A tuning fork of frequency 480Hz is used in an experiment for measuring speed of sound (v) in air by resonance tube method. Resonance is observed to occur at two successive lengths of the air column l1=30cm and l2=70cm.

Then, v is equal to

(Main 2019, 12 April II)

(a) 332ms1

(b) 384ms1

(c) 338ms1

(d) 379ms1

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Answer:

Correct Answer: 1. (b)

Solution:

  1. In a resonance tube apparatus, first and second resonance occur as shown

As in a stationary wave, distance between two successive nodes is λ2 and distance of a node and an antinode is λ4.

l2l1=3λ4λ4=λ2

So, speed of sound, v=fλ=f×2(l2l1) =480×2×(7030)×102=384ms1



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