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(a) If the amplitude in a sound wave is tripled, by what factor does the intensity of the wave increase? (b) By what factor must the amplitude of a sound wave be decreased in order to decrease the intensity by a factor of \(3 ?\)

Short Answer

Expert verified
(a) The intensity increases by a factor of 9. (b) Amplitude must decrease by a factor of \( \sqrt{3} \) to reduce intensity by 3.

Step by step solution

01

Understand the Relationship

The intensity ( I ) of a sound wave is proportional to the square of its amplitude ( A ). This can be expressed as I 鈭 A^2.
02

Determine the Intensity Increase Factor

When the amplitude is tripled ( A 鈫 3A ), the intensity becomes I' 鈭 (3A)^2 = 9A^2 . Therefore, the intensity increases by a factor of 9.
03

Understand the Intensity Decrease Factor

To decrease the intensity by a factor of 3, we need to find the new amplitude A ' which satisfies I' = I/3 . This implies I' 鈭 (A')^2 = A^2/3 .
04

Solve for the Amplitude Decrease Factor

If (A')^2 = A^2/3 , then A' = A/鈭3 . Thus, the amplitude must be decreased by a factor of 鈭3 to decrease the intensity by a factor of 3.

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Key Concepts

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

Amplitude and Intensity Relationship
In understanding how sound waves behave, one fundamental relationship is between amplitude and intensity. Intensity, denoted as \(I\), refers to the power carried by the sound wave per unit area. It is a measure of how much energy the wave transmits. When it comes to amplitude, symbolized as \(A\), this describes the maximum extent of the wave's oscillations. One key principle to note is that intensity is proportional to the square of the amplitude. Mathematically, this relationship is expressed as \(I \propto A^2\). This means that small changes in amplitude can lead to significant changes in intensity. For instance, doubling the amplitude would result in an intensity that is four times greater, showcasing the quadratic relationship.
Intensity Calculation
To calculate the change in intensity, we start by identifying how the amplitude has changed. If a sound wave鈥檚 amplitude is altered, the corresponding change in intensity can be determined using the relationship \(I \propto A^2\). For example, when the amplitude is tripled, you calculate the new intensity as follows:
  • Replace \(A\) with \(3A\) in the intensity formula: \((3A)^2 = 9A^2\).
  • This indicates that the intensity increases by a factor of 9.
Thus, in practical terms, if a sound wave with an amplitude of 1 unit results in an intensity of 1 unit, tripling the amplitude leads to an intensity of 9 units. This calculation illustrates the dramatic effect changing amplitude has on the intensity of sound waves.
Amplitude Decrease
Sometimes, it is necessary to reduce the intensity of a sound wave. To do this, you might lower the wave's amplitude. The relationship \(I \propto A^2\) helps us understand how much we need to decrease the amplitude to achieve a target intensity. If we want the intensity to drop by a specific factor, such as 3, we solve for the new amplitude \(A'\) such that \((A')^2 = A^2/3\). Solving this equation, we find \(A' = A/\sqrt{3}\). Therefore, by reducing the original amplitude by a factor of \(\sqrt{3}\), we achieve a decrease in intensity by a factor of 3. This method showcases how mathematical principles can be used to tailor sound waves to specific needs.
Intensity Factor Changes
Understanding how intensity changes further facilitates control over sound environments. As amplitude alterations impact intensity by squared proportion, recognizing this can be crucial in settings such as acoustics, audio engineering, and sound design. For any given factor change in intensity, the amplitude change can be derived since an increase or decrease in amplitude follows the root of the intensity factor. For example:
  • If intensity is to be increased by a factor of 16, amplitude needs to be doubled: \(A' = 2A\).
  • Conversely, if intensity is decreased by a factor of 16, then amplitude is halved: \(A' = A/2\).
In operations where precise control of wave properties is crucial, such awareness of the relationships between amplitude and intensity is essential in achieving the desired outcomes.

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