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Question 31281
JEE Physics · Hard

Sound Waves: Resonance Advanced MCQ

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Resonance AdvancedHardQuestion 31281

Question

In a Kundt's tube, cork dust forms heaps at nodes of the standing wave. If the frequency is 2 kHz and the distance between alternate heaps is 8 cm, speed of sound in the gas is:
  1. A
    160 m/s
  2. B
    320 m/s
    Correct
  3. C
    640 m/s
  4. D
    80 m/s

Correct answer

320 m/s

Explanation

Distance between alternate heaps = λ/2 (consecutive nodes) × 2 = λ... Heaps form at nodes. Distance between successive node positions = λ/2. Alternate heaps = every other node = λ apart. 8 cm... If alternate heaps are λ/2 apart (consecutive nodes 8 cm): λ = 16 cm = 0.16 m. v = fλ = 2000×0.16 = 320 m/s.

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