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NEET 2016 (Phase 1) · Speed of Waves

Speed of Waves question from NEET 2016 (Phase 1)

Q35NEET 2016 · PHASE 1Medium

Speed of Waves

A uniform rope of length L and mass m1 hangs vertically from a rigid support. A block of mass m2 is attached to the free end of the rope. A transverse pulse of wavelength λ\lambda1 is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is λ\lambda2. The ratio λ\lambda 2/λ\lambda1 is

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Answer: (d)

  1. Frequency stays the same, so λ∝v∝T\lambda \propto v \propto \sqrt{T}.
  2. Bottom: T1=m2gT_1 = m_2 g; top: T2=(m1+m2)gT_2 = (m_1+m_2)g.
  3. λ2λ1=m1+m2m2\dfrac{\lambda_2}{\lambda_1} = \sqrt{\dfrac{m_1+m_2}{m_2}}
  4. So the answer is (d).
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