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JEE Main 2017 (8 Apr, Shift 1) · Stationary Waves & Vibrating Strings

Stationary Waves & Vibrating Strings question from JEE Main 2017 (8 Apr, Shift 1)

Q99JEE Main 2017 · 8 APR · SHIFT 1Difficult

Stationary Waves & Vibrating Strings

Two wires W1 and W2 have the same radius r and respective densities ρ\rho1 and ρ\rho2 such that ρ2 = 4ρ\rho1. They are joined together at the point O, as shown in the figure. The combination is used as a sonometer wire and kept under tension T. The point O is midway between the two bridges. When a stationary wave is set up in the composite wire, the joint is found to be a node. The ratio of the number of antinodes formed in W1 to W2 is:

Figure

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Answer: (b)

  1. Same radius: μ∝ρ\mu \propto \rho, so μ2=4μ1\mu_2=4\mu_1 and v1=2v2v_1=2v_2.
  2. Equal lengths, same frequency, joint a node: p∝1vp \propto \frac{1}{v}.
  3. p1:p2=1:2p_1:p_2=1:2, so the answer is (b).
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