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JEE Main 2019 (8 Apr, Shift 1) · Stationary Waves & Vibrating Strings

Stationary Waves & Vibrating Strings question from JEE Main 2019 (8 Apr, Shift 1)

Q97JEE Main 2019 · 8 APR · SHIFT 1Difficult

Stationary Waves & Vibrating Strings

Figure

A wire of length 2L, is made by joining two wires A and B of same length but different radii r and 2r and made of the same material. It is vibrating at a frequency such that the joint of the two wires forms a node. If the number of antinodes in wire A is p and that in B is q then the ratio p: q is:

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Answer: (c)

  1. Radii rr and 2r2r: μB=4μA\mu_B=4\mu_A, so vA=2vBv_A=2v_B.
  2. Same ff, same length LL, joint a node: f=pvA2L=qvB2Lf=\frac{p v_A}{2L}=\frac{q v_B}{2L}.
  3. pq=vBvA=12\frac{p}{q}=\frac{v_B}{v_A}=\frac{1}{2}, so the answer is (c) 1:21:2.
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