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QJEEM20Phb887: JEE Main 2020 Physics - Class 12 JEEM20Phb887 Solution: Two coherent sources of sound, S 1 and S 2 , produce sound…

Two coherent sources of sound, S1 and S2, produce sound waves of the same wavelength, λ\lambda = 1 m, in phase. S1 and S2 are placed 1.5 m apart (see fig). A listener, located at L, directly in front of S2 finds that the intensity is at a minimum
when he is 2 m away from S2. The listener moves away from S1, keeping his distance from S2 fixed. The adjacent maximum of intensity is observed when the listener is at a distance d from S1. Then, d is : JEE Main 2020 (Online) 5th September Evening Slot Physics - Wave Optics Question 89 English

Multiple Choice Options

  • A 12 m
  • B 2 m
  • C 3 m
  • D 5 m

Step-by-Step Verified Solution

JEE Main 2020 (Online) 5th September Evening Slot Physics - Wave Optics Question 89 English Explanation

Initially S2L = 2 m

S1L = 22+(1.5)2\sqrt {{2^2} + {{\left( {1.5} \right)}^2}} = 2.5 m

For minimum at (L)

S1L – S2L = Δ\Delta x = (2n+1)λ2\left( {2n + 1} \right){\lambda \over 2}

⇒\Rightarrow 2.5 - 2 = (2n+1)12\left( {2n + 1} \right){1 \over 2}

⇒\Rightarrow 0.5 = (2n+1)2{{\left( {2n + 1} \right)} \over 2}

⇒\Rightarrow 1 = 2n + 1

⇒\Rightarrow n = 0 (first minima)

so at P →\to first maxima

∴\therefore S1P – S2P = n λ\lambda = 1 λ\lambda

⇒\Rightarrow d - 2 = 1

⇒\Rightarrow d = 3 m

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