Waves & Sound · JEE Main previous year questions

2020 5 questions

1. Q452020 · 6 Sept 2020 · Shift 1
   
   1. A.
   2. B.
   3. C.
   4. D.
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   Answer: D

2. Q422020 · 9 Jan 2020 · Shift 1

   Three harmonic waves having equal frequency $\nu$ and same intensity $I_0$, have phase angles $0$, $\frac{\pi }{4}$ and $-\frac{\pi }{4}$ respectively. When they are superimposed the intensity of the resultant wave is close to :

   1. A.$5.8I_0$
   2. B.$3I_0$
   3. C.$0.2I_0$
   4. D.$I_0$
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   Answer: A

3. Q502020 · 8 Jan 2020 · Shift 1· Numerical answer

   A one metre long (both ends open) organ pipe is kept in a gas that has double the density of air at STP. Assuming the speed of sound in air at STP is 300 m/s, the frequency difference between the fundamental and second harmonic of this pipe is ________ Hz.

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   Answer: 105.75 to 106.07

4. Q332020 · 8 Jan 2020 · Shift 2

   A transverse wave travels on a taut steel wire with a velocity of v when tension in it is $2.06\times 10^4\text{ N}$. When the tension is changed to T, the velocity changed to v/2. The value of T is close to :

   1. A.$30.5\times 10^4\text{ N}$
   2. B.$2.50\times 10^4\text{ N}$
   3. C.$10.2\times 10^2\text{ N}$
   4. D.$5.15\times 10^3\text{ N}$
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   Answer: D

5. Q452020 · 7 Jan 2020 · Shift 2

   A stationary observer receives sound from two identical tuning forks, one of which approaches and the other one recedes with the same speed (much less than the speed of sound). The observer hears 2 beats/sec. The oscillation frequency of each tuning fork is ${\nu }_0=1400\text{ Hz}$ and the velocity of sound in air is $350\text{ m/s}$. The speed of each tuning fork is close to :

   1. A.1 m/s
   2. B.$\frac{1}{8}\text{ m/s}$
   3. C.$\frac{1}{4}\text{ m/s}$
   4. D.$\frac{1}{2}\text{ m/s}$
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   Answer: C