Question

Difficulty: MediumProduction, Propagation, and Classification of Waves

A longitudinal mechanical wave propagates through a gas at a speed of 340 m/s340\text{ m/s}. If a particle in the gas completes 5050 full oscillations in 0.10 s0.10\text{ s}, what is the distance between a compression and the immediate next rarefaction?

  1. 0.34 m0.34\text{ m}Answer
  2. B
    0.68 m0.68\text{ m}
  3. C
    1.70 m1.70\text{ m}
  4. D
    1.36 m1.36\text{ m}

Answer

The distance between a compression and the adjacent rarefaction is 0.34 m0.34\text{ m}.
The frequency of the particle oscillation is f=50/0.10=500 Hzf = 50 / 0.10 = 500\text{ Hz}. Using the wave equation v=fλv = f\lambda, the wavelength λ=340/500=0.68 m\lambda = 340 / 500 = 0.68\text{ m}. Because a compression and the consecutive rarefaction represent half of a full wave cycle, the distance between them is λ/2=0.34 m\lambda / 2 = 0.34\text{ m}.

Step-by-Step Solution

1
Calculate the frequency of oscillation of the wave
f=Number of oscillationsTime interval=500.10 s=500 Hzf = \frac{\text{Number of oscillations}}{\text{Time interval}} = \frac{50}{0.10\text{ s}} = 500\text{ Hz}
Frequency is defined as the number of complete vibrations per unit time.
2
Calculate the wavelength using the wave equation
λ=vf=340 m/s500 Hz=0.68 m\lambda = \frac{v}{f} = \frac{340\text{ m/s}}{500\text{ Hz}} = 0.68\text{ m}
The fundamental wave equation relates speed, frequency, and wavelength.
3
Determine the distance between consecutive compression and rarefaction
d=λ2=0.68 m2=0.34 md = \frac{\lambda}{2} = \frac{0.68\text{ m}}{2} = 0.34\text{ m}
In a longitudinal wave, a compression and the nearest rarefaction are separated by half a wavelength.

Key Concept

Relation between frequency, wavelength, wave speed, and structural intervals in longitudinal waves
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