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NTA Abhyas JEE Main2020PhysicsWaves and SoundPractice

An open pipe is in resonance in 2 nd harmonic with frequency f 1 . Now one end of the tube is closed and frequency is increased to f 2 such that the resonance again occurs in n th harmonic. Choose the correct option.

Options

  1. An = 3 , f ⁡ 2 = 3 4 f ⁡ 1
  2. Bn = 3 , f ⁡ 2 = 5 4 f ⁡ 1
  3. Cn = 5 , f ⁡ 2 = 5 4 f ⁡ 1
  4. Dn = 5 , f ⁡ 2 = 3 4 f ⁡ 1

Correct answer

C. n = 5 , f ⁡ 2 = 5 4 f ⁡ 1

Step-by-step solution

f ⁡ 1 = v ⁡ l ⁡ (2nd harmonic of open pipe) f ⁡ 2 = n v ⁡ 4 l ⁡ (nth harmonic of closed pipe) Here, n is odd and f ⁡ 2 > f ⁡ 1 It is possible when n = 5 because with n = 5 f ⁡ 2 = 5 4 v ⁡ l ⁡ = 5 4 f ⁡ 1

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