Waves & Sound · JEE Main previous year questions

2025 4 questions

1. Q332025 · 8 Apr 2025 · Shift 2

   The amplitude and phase of a wave that is formed by the superposition of two harmonic travelling waves, $y_1(x,t)=4\sin (kx-\omega t)$ and $y_2(x,t)=2\sin (kx-\omega t+\frac{2\pi }{3})$, are: (Take the angular frequency of initial waves same as $\omega$)

   1. A.$\left[\sqrt{3},\frac{\pi }{6}\right]$
   2. B.$\left[2\sqrt{3},\frac{\pi }{6}\right]$
   3. C.$\left[6,\frac{2\pi }{3}\right]$
   4. D.$\left[6,\frac{\pi }{3}\right]$
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   Answer: B

2. Q262025 · 4 Apr 2025 · Shift 1

   Consider the sound wave travelling in ideal gases of $\mathrm{He}$, $\mathrm{C}{\mathrm{H}}_4$, and $\mathrm{C}{\mathrm{O}}_2$. All the gases have the same ratio $\frac{P}{\rho }$, where $P$ is the pressure and $\rho$ is the density. The ratio of the speed of sound through the gases $V_{\mathrm{He}}:V_{\mathrm{C}{\mathrm{H}}_4}:V_{\mathrm{C}{\mathrm{O}}_2}$ is given by

   1. A.$\sqrt{\frac{7}{5}}:\sqrt{\frac{5}{3}}:\sqrt{\frac{4}{3}}$
   2. B.$\sqrt{\frac{5}{3}}:\sqrt{\frac{4}{3}}:\sqrt{\frac{4}{3}}$
   3. C.$\sqrt{\frac{5}{3}}:\sqrt{\frac{4}{3}}:\sqrt{\frac{7}{5}}$
   4. D.$\sqrt{\frac{4}{3}}:\sqrt{\frac{5}{3}}:\sqrt{\frac{7}{5}}$
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   Answer: C

3. Q372025 · 4 Apr 2025 · Shift 1

   In an experiment with a closed organ pipe, it is filled with water by $(\frac{1}{5})$ th of its volume. The frequency of the fundamental note will change by

   1. A.$20\%$
   2. B.$25\%$
   3. C.$-20\%$
   4. D.$-25\%$
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   Answer: B

4. Q352025 · 3 Apr 2025 · Shift 2

   In the resonance experiment, two air columns (closed at one end) of $100\mathrm{cm}$ and $120\mathrm{cm}$ long, give $15$ beats per second when each one is sounding in the respective fundamental modes. The velocity of sound in the air column is:

   1. A.$370m/s$
   2. B.$340m/s$
   3. C.$335m/s$
   4. D.$360m/s$
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   Answer: D