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What phase difference between two identical traveling waves, moving in the same direction along a stretched string, results in the combined wave having an amplitude \(0.852\) times that of the common amplitude of the two combining waves? Express your answer in (a) degrees, (b) radians, and (c) wavelengths.

Short Answer

Expert verified
The phase difference is approximately 129.33° or 2.258 radians or 0.359 wavelengths.

Step by step solution

01

Understanding the Problem

We need to find the phase difference between two identical traveling waves that results in the combined wave's amplitude being 0.852 times the original amplitude of the individual waves. The relationship for the resultant amplitude of two waves is given by the formula \( A_R = 2A \cos(\frac{\Delta \phi}{2}) \), where \(A_R\) is the resultant amplitude, \(A\) is the common amplitude, and \( \Delta \phi \) is the phase difference.
02

Setting Up the Equation

Given that the resultant amplitude is 0.852 times the common amplitude, we can write the equation \( 2A \cos(\frac{\Delta \phi}{2}) = 0.852A \). Dividing both sides by \(2A\), we get \( \cos(\frac{\Delta \phi}{2}) = 0.426 \).
03

Solving for the Phase Difference (Radians)

To find \( \Delta \phi \), we first solve for \(\frac{\Delta \phi}{2}\) by taking the inverse cosine (arccos) of 0.426. Therefore, \( \frac{\Delta \phi}{2} = \arccos(0.426) \). Calculating this gives \( \frac{\Delta \phi}{2} \approx 1.129 \) radians. Thus, \( \Delta \phi \approx 2.258 \) radians.
04

Converting to Degrees

To convert radians to degrees, we use the formula \( \Delta \phi_{\text{degrees}} = \Delta \phi_{\text{radians}} \times \frac{180}{\pi} \). Substituting \(2.258 \) radians, we find \( \Delta \phi \approx 129.33 \) degrees.
05

Finding Phase Difference in Wavelengths

Phase difference in terms of wavelengths is given by \( \frac{\Delta \phi}{2\pi} \). Substituting \( \Delta \phi = 2.258 \) radians, we find \( \Delta \phi_{\text{wavelengths}} = \frac{2.258}{2\pi} \approx 0.359 \) wavelengths.

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Key Concepts

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

Phase Difference
Phase difference refers to the difference in the phase angle between two waves. When two waves travel together, their phase difference determines the way they combine. If their phases are in sync, they will constructively interfere, resulting in a larger amplitude. Conversely, if they are out of sync by certain amounts, they destructively interfere, diminishing the resultant amplitude. The formula that describes the resultant amplitude of two waves is given by:\[ A_R = 2A \cos\left(\frac{\Delta \phi}{2}\right) \]Here, \( A_R \) is the resultant amplitude, \( A \) is the common amplitude of the waves, and \( \Delta \phi \) is the phase difference. Therefore, by manipulating \( \Delta \phi \), we can control how the waves interact with each other. In the given exercise, you found the necessary phase difference for the resultant amplitude to be 0.852 times the common amplitude. This highlights the impactful role of phase difference in wave interference.
Amplitude
Amplitude is a measure of the maximum displacement or distance that the points on a wave (such as sound waves, light waves, etc.) move from their rest position. Amplitude is directly related to the energy carried by the wave; a higher amplitude wave can transfer more energy. In the context of wave interference, when two waves combine, their amplitudes add up in a way that depends on their relative phases. If two identical waves are perfectly in phase, their amplitudes add positively, resulting in a higher overall amplitude. However, if they are out of phase, the waves can partially or completely cancel each other out, leading to reduced or zero amplitude. In our exercise, the resultant amplitude was desired to be 0.852 of the common amplitude. This shows partial destructive interference due to the specific phase difference employed.
Radians
Radians are a unit of angle measurement widely used in mathematics and physics. Unlike degrees, radians provide a more natural way to express angles in the context of wave motion and circular changes. One complete cycle around a circle is equivalent to \( 2\pi \) radians, the basis for most of wave phase calculations.To convert from radians to degrees, we use the equation:\[ \text{Degrees} = \text{Radians} \times \frac{180}{\pi} \]Radians allow for easy calculations in wave interference, especially when working with trigonometric functions such as cosine and sine. For example, in our exercise, we used radians to determine the phase difference that yielded a specific wave interference pattern.
Degrees
Degrees are a more commonly known unit for measuring angles, with one complete rotation of a circle being equal to 360 degrees. In many practical applications and discussions, degrees are used for their simplicity.The conversion from radians to degrees can be crucial when analyzing wave interference phenomena. For the exercise, after calculating the phase difference in radians, we converted this into degrees to yield a more intuitive understanding:\[ \text{Degrees} = \text{Radians} \times \frac{180}{\pi} \]This resulted in a phase difference of approximately 129.33 degrees, demonstrating the level of precision necessary for accurately describing wave interactions in everyday terms. Using degrees can make it easier to visualize the changes in wave patterns and interference outcomes.

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Most popular questions from this chapter

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