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A sound wave in air has a frequency of \(425 \mathrm{Hz}\). (a) What is its wavelength? (b) If the frequency of the sound is increased, does its wavelength increase, decrease, or stay the same? Explain, \((c)\) Calculate the wavelength for a sound wave with a frequency of \(475 \mathrm{Hz}\)

Short Answer

Expert verified
(a) 0.807 m, (b) wavelength decreases, (c) 0.722 m.

Step by step solution

01

Understanding the relationship between frequency and wavelength

Sound travels through air with speed denoted by \(v\). The formula to find the wavelength \(\lambda\) is \(\lambda = \frac{v}{f}\), where \(v\) is the speed of sound in air (approximately \(343\, \text{m/s}\) at room temperature) and \(f\) is the frequency in Hertz (Hz).
02

Calculate the wavelength for 425 Hz

Using the formula \(\lambda = \frac{v}{f}\), we substitute the known values, \(v = 343\, \text{m/s}\) and \(f = 425\, \text{Hz}\):\[\lambda = \frac{343\, \text{m/s}}{425\, \text{Hz}} \approx 0.807\, \text{m}\]Thus, the wavelength for a frequency of \(425\, \text{Hz}\) is approximately \(0.807\, \text{m}\).
03

Determine wavelength change when frequency changes

When the frequency of a sound wave increases, according to the formula \(\lambda = \frac{v}{f}\), the wavelength \(\lambda\) decreases because the speed of sound \(v\) remains constant.
04

Calculate the wavelength for 475 Hz

Now, to find the wavelength for a frequency of \(475\, \text{Hz}\), we use the same formula:\[\lambda = \frac{343\, \text{m/s}}{475\, \text{Hz}} \approx 0.722\, \text{m}\]Hence, the wavelength for a sound wave with a frequency of \(475\, \text{Hz}\) is approximately \(0.722\, \text{m}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Wavelength Calculation
Wavelength is an important characteristic of sound waves. It refers to the distance between successive crests or troughs, specifically, how far apart the wave fronts of the sound are from each other. To calculate wavelength, we use a simple formula:
  • \(\lambda = \frac{v}{f}\)
Here, \(\lambda\) represents the wavelength in meters, \(v\) is the speed of sound in the medium (in meters per second), and \(f\) is the frequency of the sound wave in Hertz.
For example, if a sound wave in air has a speed of \(343 \, \text{m/s}\), which is typical at room temperature, and a frequency of \(425 \, \text{Hz}\), the wavelength would be calculated as follows:
  • Substitute the known values: \(\lambda = \frac{343 \, \text{m/s}}{425 \, \text{Hz}}\).
  • The result is approximately \(0.807 \, \text{meters}\).
This gives us an understanding of how frequent waves are spaced out in this given frequency.
Speed of Sound
The speed of sound is crucial in understanding sound wave behavior. It is the rate at which sound waves propagate through a medium. Sound travels at different speeds depending on the medium -- air, water, or solids are common mediums. At room temperature, the speed of sound in air is approximately \(343 \, \text{m/s}\).
Several factors influence the speed of sound:
  • Medium: Sound travels faster in water and even faster in solids than in air.
  • Temperature: Generally, the speed increases with higher temperatures in a given medium.
  • Pressure li>Density of the medium.

Understanding the speed of sound helps in determining other properties such as wavelength if frequency is known, or frequency if wavelength is known, using their relationship with speed.
Frequency-Wavelength Relationship
The relationship between frequency and wavelength is inverse and fundamental to wave physics. The formula \(\lambda = \frac{v}{f}\) highlights this. If the speed of sound \(v\) is constant, as it generally is in a given medium and conditions, changes in frequency \(f\) lead to opposite changes in wavelength \(\lambda\).
  • If frequency increases, wavelength decreases.
  • If frequency decreases, wavelength increases.
This concept explains why different frequencies result in different perceptions of sound, like pitch.
For example, increasing the frequency from \(425 \, \text{Hz}\) to \(475 \, \text{Hz}\) results in a wavelength change from approximately \(0.807 \, \text{m}\) to \(0.722 \, \text{m}\). The decrease in wavelength corresponds with the increase in frequency, illustrating their inversely proportional relationship.

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Most popular questions from this chapter

A train on one track moves in the same direction as a second train on the adjacent track. The first train, which is ahead of the second train and moves with a speed of \(36.8 \mathrm{m} / \mathrm{s},\) blows a horn whose frequency is \(124 \mathrm{Hz}\). If the frequency heard on the second train is \(135 \mathrm{Hz},\) what is its speed?

A rope of length \(L\) and mass \(M\) hangs vertically from a ceiling. The tension in the rope is only that due to its own weight. (a) Suppose a wave starts near the bottom of the rope and propagates upward. Does the speed of the wave increase, decrease, or stay the same as it moves up the rope? Explain. (b) Show that the speed of waves a height \(y\) above the bottom of the rope is \(v=\sqrt{g y}\)

A tuning fork with a frequency of \(320.0 \mathrm{Hz}\) and a tuning fork of unknown frequency produce beats with a frequency of \(4.5 \mathrm{Hz} .\) If the frequency of the \(320.0-\mathrm{H} z\) fork is lowered slightly by placing a bit of putty on one of its tines, the new beat frequency is \(7.5 \mathrm{Hz}\) (a) Which tuning fork has the lower frequency? Explain. (b) What is the final frequency of the \(320.0-11 z\) tuning fork? (c) What is the frequency of the other tuning fork?

CE The vertical displacement of a wave on a string is described by the equation \(y(x, t)=A \sin (B x+C t),\) in which \(A, B\) and \(C\) are positive constants. (a) Docs this wave propagate in the positive or negative \(x\) direction? (b) What is the physical meaning of the constant \(A\) ? (c) What is the speed of this wave? (d) What is the smallest positive time \(f\) for which the wave has zero displacement at the point \(x=0 ?\)

You stand near the tracks as a train approaches with constant speed. The train is operating its horn continuously, and you listen carefully to the sound it makes. For each of the following properties of the sound, state whether it increases, decreases, or stays the same as the train gets closer: (a) the intensity; (b) the frequency; (c) the wavelength; (d) the speed.

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