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NEET 1990 (AIPMT) · Progressive Wave Equation

Progressive Wave Equation question from NEET 1990 (AIPMT)

Q108NEET 1990 · AIPMTEasy

Progressive Wave Equation

Velocity of sound waves in air is 330 m/s330\text{ m/s}. For a particular sound wave in air, a path difference of 40 cm40\text{ cm} is equivalent to phase difference of 1.6π1.6\pi. The frequency of this wave is

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Answer: (c)

  1. Δϕ=2πλΔx⇒1.6π=2π(0.4)λ\Delta\phi = \frac{2\pi}{\lambda}\Delta x \Rightarrow 1.6\pi = \frac{2\pi(0.4)}{\lambda}
  2. λ=0.81.6=0.5 m\lambda = \frac{0.8}{1.6} = 0.5\text{ m}
  3. f=vλ=3300.5=660 Hzf = \frac{v}{\lambda} = \frac{330}{0.5} = 660\text{ Hz}
  4. So the answer is (c) 660 Hz660\text{ Hz}.
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