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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Sound Waves

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Sound Waves

Determine the frequency of beats produced in air when two sources...

Determine the frequency of beats produced in air when two sources of sound are activated, with one emitting a wavelength of 32 cm32 \text{ cm} and the other a wavelength of 32.2 cm32.2 \text{ cm}. The speed of sound in air is 350 m/s350 \text{ m/s}.

Options

  1. A7 Hz7 \text{ Hz}
  2. B14 Hz14 \text{ Hz}
  3. C3 Hz3 \text{ Hz}
  4. D0.07 Hz0.07 \text{ Hz}

Correct answer

A. 7 Hz7 \text{ Hz}

Step-by-step solution

Given:

Speed of sound, v=350 m/sv = 350 \text{ m/s}

Wavelength of first source, λ1=32 cm=0.32 m\lambda_1 = 32 \text{ cm} = 0.32 \text{ m}

Wavelength of second source, λ2=32.2 cm=0.322 m\lambda_2 = 32.2 \text{ cm} = 0.322 \text{ m}

The frequencies of the sound produced by the two sources are:

f1=vλ1=3500.32=1093.75 Hzf_1 = \dfrac{v}{\lambda_1} = \dfrac{350}{0.32} = 1093.75 \text{ Hz}

f2=vλ2=3500.322≈1086.96 Hzf_2 = \dfrac{v}{\lambda_2} = \dfrac{350}{0.322} \approx 1086.96 \text{ Hz}

The beat frequency is the difference between the two frequencies:

fbeat=f1−f2=1093.75−1086.96=6.79 Hzf_{beat} = f_1 - f_2 = 1093.75 - 1086.96 = 6.79 \text{ Hz}

Rounding to the nearest integer, the beat frequency is approximately 7 Hz7 \text{ Hz}.
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