/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 23 (1) Suppose at \(t=0,\) a wave s... [FREE SOLUTION] | 91Ó°ÊÓ

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(1) Suppose at \(t=0,\) a wave shape is represented by \(D=A \sin (2 \pi x / \lambda+\phi) ;\) that is, it differs from Eq. 9 by a constant phase factor \(\phi .\) What then will be the equation for a wave traveling to the left along the \(x\) axis as a function of \(x\) and \(t ?\)

Short Answer

Expert verified
The wave equation is \(D(x,t) = A \sin \left( \frac{2\pi}{\lambda}x + \frac{2\pi v}{\lambda}t + \phi \right)\).

Step by step solution

01

Understanding Wave Equation

The given wave equation is \(D = A \sin \left( \frac{2\pi x}{\lambda} + \phi \right)\), which represents a wave at time \(t=0\). In this equation, \(A\) is the amplitude, \(\lambda\) is the wavelength, and \(\phi\) is the phase constant.
02

General Wave Equation for Leftward Movement

For a wave traveling to the left, the general equation is \(D(x,t) = A \sin \left( \frac{2\pi}{\lambda}(x + vt) + \phi \right)\), where \(v\) is the wave speed.
03

Adjust the General Equation for Given Conditions

Incorporate the phase factor \(\phi\) from the problem into the general wave equation. Thus, for a wave traveling left, the equation becomes \(D(x,t) = A \sin \left( \frac{2\pi}{\lambda}(x + vt) + \phi \right)\).
04

Final Equation

The final equation for a wave traveling to the left is thus \(D(x,t) = A \sin \left( \frac{2\pi}{\lambda}x + \frac{2\pi v}{\lambda}t + \phi \right)\).

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Key Concepts

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

Amplitude
The amplitude of a wave is one of its most critical characteristics. It is represented by the letter \(A\) in the wave equation. Amplitude refers to the maximum height of the wave from its equilibrium position. When you visualize a wave, amplitude is essentially the "tallness" or "depth" of the wave crest or trough.

Amplitude is important because it helps you understand the energy of the wave. Higher amplitude waves carry more energy. For instance, in the case of sound waves, a larger amplitude results in a louder sound. For light waves, higher amplitude means brighter light.

In the equation \(D = A \sin \left(\frac{2\pi x}{\lambda} + \phi \right)\), \(A\) remains constant and signifies how far the particles in the medium move from their rest position due to the wave. It's helpful to remember:
  • The greater the amplitude, the more energetic the wave.
  • Amplitude is always a positive value, even though the wave itself may dip below the equilibrium line.
  • In the real world, amplitude can be affected by factors such as the medium through which the wave travels.
Wavelength
Wavelength, denoted by \(\lambda\), is another essential feature of a wave, dictating the spatial period of the wave—the distance over which the wave shape repeats. In the wave equation \(D = A \sin \left(\frac{2\pi x}{\lambda} + \phi \right)\), wavelength is critical in defining how frequently the wave cycles occur along the \(x\)-axis.

You can think of wavelength as the length of one complete wave cycle. It's measured as the distance between two consecutive points in phase, such as crest to crest or trough to trough. Wavelengths explain how "spread out" or "squeezed together" waves appear.

Wavelength has practical applications across various disciplines:
  • In optics, wavelength determines the color of light—shorter wavelengths appear blue, and longer ones appear red.
  • In water waves, wavelength influences the wave's behavior when interacting with obstacles.
  • For electromagnetic waves, different wavelengths belong to different segments of the electromagnetic spectrum, such as microwaves or X-rays.
Wavelength is inversely related to frequency, meaning that waves with long wavelengths have lower frequencies and vice versa.
Phase Constant
The phase constant \(\phi\) in the wave equation \(D = A \sin \left(\frac{2\pi x}{\lambda} + \phi \right)\) adds an intriguing layer of complexity by introducing a phase shift. Phase constant acts like a manual "tweak" in the positioning of the wave.

Think of the phase as the process of adjusting the wave's starting point. It's like rotating the wave along its axis without altering its size or shape. In practical terms, a non-zero phase constant displaces the wave left or right along the \(x\)-axis.

The phase constant connects to how different waves might interact with each other. If two waves have different phases, they might "add up" (constructive interference) or "cancel out" (destructive interference), depending on their phase difference. Remember these points about the phase constant:
  • Phase constant does not affect wave amplitude or wavelength.
  • If \(\phi = 0\), the wave starts at the origin of its cycle.
  • The value of \(\phi\) can range from \(-\pi\) to \(\pi\), effectively modifying where the wave begins in its cycle.
This parameter is essential when synchronizing waves in physics, electronics, or engineering applications.

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Most popular questions from this chapter

(II) (a) Show that the average rate with which energy is transported along a cord by a mechanical wave of frequency \(f\) and amplitude \(A\) is $$\bar{P}=2 \pi^{2} \mu v f^{2} A^{2}$$ where \(v\) is the speed of the wave and \(\mu\) is the mass per unit length of the cord. (b) If the cord is under a tension \(F_{\mathrm{T}}=135 \mathrm{~N}\) and has mass per unit length \(0.10 \mathrm{~kg} / \mathrm{m},\) what power is required to transmit \(120-\mathrm{Hz}\) transverse waves of amplitude \(2.0 \mathrm{~cm} ?\)

(II) The intensity of an earthquake wave passing through the Earth is measured to be \(3.0 \times 10^{6} \mathrm{~J} / \mathrm{m}^{2} \cdot \mathrm{s}\) at a distance of \(48 \mathrm{~km}\) from the source. (a) What was its intensity when it passed a point only \(1.0 \mathrm{~km}\) from the source? \((b)\) At what rate did energy pass through an area of \(2.0 \mathrm{~m}^{2}\) at \(1.0 \mathrm{~km} ?\)

(II) Determine if the function \(D=A \sin k x \cos \omega t\) is a solution of the wave equation.

(II) A sound wave is traveling in warm air \(\left(25^{\circ} \mathrm{C}\right)\) when it hits a layer of cold \(\left(-15^{\circ} \mathrm{C}\right)\) denser air. If the sound wave hits the cold air interface at an angle of \(33^{\circ},\) what is the angle of refraction? The speed of sound as a function of temperature can be approximated by \(v=(331+0.60 T) \mathrm{m} / \mathrm{s},\) where \(T\) is in \({ }^{\circ} \mathrm{C}\).

(II) \(\mathrm{P}\) and \(\mathrm{S}\) waves from an earthquake travel at different speeds, and this difference helps locate the earthquake "epicenter" (where the disturbance took place). (a) Assuming typical speeds of 8.5 \(\mathrm{km} / \mathrm{s}\) and 5.5 \(\mathrm{km} / \mathrm{s}\) for \(\mathrm{P}\) and \(\mathrm{S}\) waves, respectively, how far away did the earthquake occur if a particular seismic station detects the arrival of these two types of waves 1.7 min apart? (b) Is one seismic station sufficient to determine the position of the epicenter? Explain.

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