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Superposition and Interference Two waves in one string are described by the wave functions $$ y_{1}=3.0 \cos (4.0 x-1.6 t) $$ and $$ y_{2}=4.0 \sin (5.0 x-2.0 t) $$ where \(y\) and \(x\) are in centimeters and \(t\) is in seconds. Find the superposition of the waves \(y_{1}+y_{2}\) at the points (a) \(x=1.00\) \(t=1.00,\) (b) \(x=1.00, t=0.500,\) and \((\mathrm{c}) x=0.500, t=0\) (Remember that the arguments of the trigonometric functions are in radians.)

Short Answer

Expert verified
To solve superposition and interference problems, one needs to find the sum of the individual wave functions. Here, the interference of \(y_1\) and \(y_2\) at \((x,y)\) can be found by substituting the values of \(x\) and \(t\) into the superposition equation, \(y = y_1 + y_2 = 3.0 \cos (4.0x - 1.6t) + 4.0 \sin (5.0x - 2.0t)\), and computing the resulting expression.

Step by step solution

01

Define the Superposition

The superposition of two waves is the sum of their individual wave functions. In this case, it is \(y = y_1 + y_2 = 3.0 \cos (4.0x - 1.6t) + 4.0 \sin (5.0x - 2.0t)\)
02

Compute the Superposition at (a) \(x=1.00, t=1.00\)

Substitute the values of x and t into the superposition equation: \(y = 3.0 \cos (4.0*1 - 1.6*1) + 4.0 \sin (5.0*1 - 2.0*1) \)\nComputing the above expression will yield the superposition at point (a)
03

Compute the Superposition at (b) \(x=1.00, t=0.500\)

Similarly, substitute the values of x and t into the superposition equation: \(y = 3.0 \cos (4.0*1 - 1.6*0.5) + 4.0 \sin (5.0*1 - 2.0*0.5)\)\nComputing the above expression will yield the superposition at point (b)
04

Compute the Superposition at (c) \(x=0.500, t=0\)

Lastly, substitute the values of x and t into the superposition equation: \(y = 3.0 \cos (4.0*0.5 - 1.6*0) + 4.0 \sin (5.0*0.5 - 2.0*0)\)\nComputing the above expression will yield the superposition at point (c)

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Key Concepts

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

Wave Interference
When two or more waves traverse the same space, they interact with each other. This interaction is known as wave interference, which can be constructive, destructive, or a complex pattern of both. Constructive interference occurs when wave crests (or troughs) from different waves align, resulting in a wave of greater amplitude. Conversely, destructive interference happens when wave crests of one wave align with the troughs of another, reducing the wave's overall amplitude.

In the given exercise, we observe the superposition of two different waves on a string. When they meet, their respective displacements combine to form the resultant wave at any point and time. This principle is imperative in fields ranging from acoustics and optics to quantum mechanics. Understanding how to add wave functions algebraically is essential for predicting the combined influence of multiple waves on a medium.
Trigonometric Functions in Physics
Trigonometric functions like sin and cos are fundamental in describing wave motion in physics. These mathematical tools allow us to model the oscillatory behaviour of waves as they travel through space and time. The general wave function often takes the form \(y = A \times \text{trig}(kx - \theta t + \text{phase})\), where \(A\) represents the amplitude, \(k\) the wave number, \(\theta\) the angular frequency, and \(\text{phase}\) is the phase constant. Specifically, the cosine function is used when a wave begins at its maximum displacement, while sine is employed when it starts from the equilibrium position.

In our exercise, these trigonometric functions are used within wave functions to describe the position of points on a vibrating string over time, allowing us to calculate the superposition at given instances.
Wave Functions
A wave function in physics describes the characteristics of a wave at any given point and time. It succinctly represents the wave's shape, amplitude, wavelength, frequency, and phase. The wave function equations provided in the exercise, \(y_{1} = 3.0 \cos (4.0 x - 1.6 t)\) and \(y_{2} = 4.0 \sin (5.0 x - 2.0 t)\), each give a mathematical description of individual waves on the string. The cos and sin functions vary between -1 and 1, perfect for demonstrating the oscillatory nature of waves.

By adding these functions together, we obtain the superposition wave function. This effectively allows us to predict the motion and interaction of waves, forming the backbone of much of modern physics. Applications of wave functions include determining sound volume at a point due to speakers in various locations or predicting the patterns seen in wave interference experiments in the lab.

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Most popular questions from this chapter

With a particular fingering, a flute plays a note with frequency \(880 \mathrm{Hz}\) at \(20.0^{\circ} \mathrm{C} .\) The flute is open at both ends. (a) Find the air column length. (b) Find the frequency it produces at the beginning of the half-time performance at a late-season American football game, when the ambient temperature is \(-5.00^{\circ} \mathrm{C}\) and the musician has not had a chance to warm up the flute.

A shower stall measures \(86.0 \mathrm{cm} \times 86.0 \mathrm{cm} \times 210 \mathrm{cm} .\) If you were singing in this shower, which frequencies would sound the richest (because of resonance)? Assume that the stall acts as a pipe closed at both ends, with nodes at opposite sides. Assume that the voices of various singers range from \(130 \mathrm{Hz}\) to \(2000 \mathrm{Hz}\). Let the speed of sound in the hot shower stall be \(355 \mathrm{m} / \mathrm{s}.\)

A student holds a tuning fork oscillating at \(256 \mathrm{Hz}\). He walks toward a wall at a constant speed of \(1.33 \mathrm{m} / \mathrm{s}\) (a) What beat frequency does he observe between the tuning fork and its echo? (b) How fast must he walk away from the wall to observe a beat frequency of \(5.00 \mathrm{Hz} ?\)

A \(0.0100-\mathrm{kg}\) wire, \(2.00 \mathrm{m}\) long, is fixed at both ends and vibrates in its simplest mode under a tension of \(200 \mathrm{N}\). When a vibrating tuning fork is placed near the wire, a beat frequency of \(5.00 \mathrm{Hz}\) is heard. (a) What could be the frequency of the tuning fork? (b) What should the tension in the wire be if the beats are to disappear?

Standing Waves in a String Fixed at Both Ends Find the fundamental frequency and the next three frequencies that could cause standing-wave patterns on a string that is \(30.0 \mathrm{m}\) long, has a mass per length of \(9.00 \times 10^{-3} \mathrm{kg} / \mathrm{m}\) and is stretched to a tension of \(20.0 \mathrm{N}.\)

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