Waves & Sound · JEE Main previous year questions

2023 9 questions

1. Q572023 · 12 Apr 2023 · Shift 1· Numerical answer

   For a certain organ pipe, the first three resonance frequencies are in the ratio of $1:3:5$ respectively. If the frequency of fifth harmonic is $405\text{ Hz}$ and the speed of sound in air is $324{\text{ ms}}^{-1}$ the length of the organ pipe is _________ $\text{m}$.

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   Answer: 1

2. Q492023 · 11 Apr 2023 · Shift 2

   A car P travelling at $20{\text{ ms}}^{-1}$ sounds its horn at a frequency of $400\text{ Hz}$. Another car Q is travelling behind the first car in the same direction with a velocity $40{\text{ ms}}^{-1}$. The frequency heard by the passenger of the car Q is approximately [Take, velocity of sound $=360{\text{ ms}}^{-1}$]

   1. A.$485\text{ Hz}$
   2. B.$514\text{ Hz}$
   3. C.$421\text{ Hz}$
   4. D.$471\text{ Hz}$
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   Answer: C

3. Q512023 · 10 Apr 2023 · Shift 1· Numerical answer

   A transverse harmonic wave on a string is given by $$y(x,t)=5\sin (6t+0.003x)$$ where x and y are in cm and t in sec. The wave velocity is ____________ ${\text{ms}}^{-1}$.

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   Answer: 20

4. Q392023 · 10 Apr 2023 · Shift 2

   For a periodic motion represented by the equation $$y=\sin \omega t+\cos \omega t$$ the amplitude of the motion is

   1. A.1
   2. B.$\sqrt{2}$
   3. C.0.5
   4. D.2
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   Answer: B

5. Q522023 · 8 Apr 2023 · Shift 1· Numerical answer

   An organ pipe $40\text{ cm}$ long is open at both ends. The speed of sound in air is $360{\text{ ms}}^{-1}$. The frequency of the second harmonic is ___________ $\text{Hz}$.

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   Answer: 900

6. Q602023 · 6 Apr 2023 · Shift 1· Numerical answer

   A person driving car at a constant speed of $15\text{ m/s}$ is approaching a vertical wall. The person notices a change of $40\text{ Hz}$ in the frequency of his car's horn upon reflection from the wall. The frequency of horn is ________ $\text{Hz}$. (Given: Speed of sound : $330\text{ m/s}$)

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   Answer: 420

7. Q432023 · 6 Apr 2023 · Shift 2

   The ratio of speed of sound in hydrogen gas to the speed of sound in oxygen gas at the same temperature is:

   1. A.$1:1$
   2. B.$1:2$
   3. C.$1:4$
   4. D.$4:1$
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   Answer: D

8. Q382023 · 1 Feb 2023 · Shift 1

   A steel wire with mass per unit length $7.0\times 10^{-3}{\text{ kg m}}^{-1}$ is under tension of $70\text{ N}$. The speed of transverse waves in the wire will be:

   1. A.$10\text{ m/s}$
   2. B.$50\text{ m/s}$
   3. C.$100\text{ m/s}$
   4. D.$200\pi \text{ m/s}$
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   Answer: C

9. Q492023 · 29 Jan 2023 · Shift 1

   A person observes two moving trains, 'A' reaching the station and 'B' leaving the station with equal speed of $30m/s$. If both trains emit sounds with frequency $300\mathrm{Hz}$, (Speed of sound: $330m/s$) approximate difference of frequencies heard by the person will be:

   1. A.10 Hz
   2. B.55 Hz
   3. C.80 Hz
   4. D.33 Hz
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   Answer: B