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Waves · Question 14

JEE Main 2025 (Online) 4th April Morning ShiftMCQEasy📈 Topic in 19% papers+4−1
1

Consider the sound wave travelling in ideal gases of He, CH4, and CO2. All the gases have the same ratio P , where P is the pressure and is the density. The ratio of the speed of sound through the gases VHe : VCH4 : VCO2 is given by

  1. 75 : 53 : 43
  2. 53 : 43 : 43
  3. 53 : 43 : 75
  4. 43 : 53 : 75

Answer

(3) 53 : 43 : 75

Solution

Speed of sound in a gas (Laplace): v = P

Same P v

He (monatomic, 3 degrees of freedom): = 53

CH4 (non-linear polyatomic, 6 degrees of freedom): = 1 + 26 = 43

CO2 (linear molecule, 5 degrees of freedom, vibrations neglected): = 1 + 25 = 75

VHe : VCH4 : VCO2 = 53 : 43 : 75

Answer: (3)

JEE Main 2025 (Online) 4th April Morning Shift

Keep practising — Waves

2

In an experiment with a closed organ pipe, it is filled with water by ( 15 )th of its volume. The frequency of the fundamental note will change by

  1. 20\%
  2. 25\%
  3. -20\%
  4. -25\%
JEE Main 2025 (Online) 4th April Morning Shift
3

Displacement of a wave is expressed as x(t)=5 (628t+ 2 )m. The wavelength of the wave when its velocity is 300 m/s is : ( =3.14)

  1. 0.33 m
  2. 0.5 m
  3. 3 m
  4. 5 m
JEE Main 2025 (Online) 4th April Evening Shift
4

In the resonance experiment, two air columns (closed at one end) of 100 cm and 120 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. 370 m/s
  2. 340 m/s
  3. 335 m/s
  4. 360 m/s
JEE Main 2025 (Online) 3rd April Evening Shift
5

A sinusoidal wave of wavelength 7.5 cm travels a distance of 1.2 cm along the x-direction in 0.3 sec. The crest P is at x = 0 at t = 0 sec and maximum displacement of the wave is 2 cm. Which equation correctly represents this wave?

  1. y = 2 (0.83x - 3.35t) cm
  2. y = 2 (0.83x - 3.5t) cm
  3. y = 2 (0.13x - 0.5t) cm
  4. y = 2 (3.35x - 0.83t) cm
JEE Main 2025 (Online) 2nd April Evening Shift
6

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R In the light of the above statements, choose the correct answer from the options given below

  1. Both A and R are true and R is the correct explanation of A
  2. A is false but R is true
  3. A is true but R is false
  4. Both A and R are true but R is NOT the correct explanation of A
JEE Main 2025 (Online) 28th January Morning Shift

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