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For the stationary wave \(y=4 \sin \left(\frac{\pi x}{15}\right) \cos (96 \pi t)\), \((x\) and \(y\) are in \(\mathrm{cm}\) and \(t\) in second) the distance between a node and the next anti-nodes is (A) \(7.5 \mathrm{~cm}\) (B) \(15 \mathrm{~cm}\) (C) \(22.5 \mathrm{~cm}\) (D) \(30 \mathrm{~cm}\)

Short Answer

Expert verified
The distance between a node and the next anti-node in the given stationary wave is 7.5 cm.

Step by step solution

01

Identify the term for the displacement

In the given wave equation \(y = 4 \sin\left(\frac{\pi x}{15}\right) \cos(96\pi t)\), the displacement is represented by the term \(\sin\left(\frac{\pi x}{15}\right)\).
02

Find the position of a node

A node occurs when there is zero displacement. So, we set the displacement term equal to zero and solve for x: \(\sin\left(\frac{\pi x}{15}\right) = 0\) The general solution for x can be given as: \(x = 15n\), where n is an integer Let's consider n = 0 and n = 1. When n = 0, \(x = 15(0) = 0\) When n = 1, \(x = 15(1) = 15\) The first node is at x = 0 cm and the second node is at x = 15 cm.
03

Find the position of an anti-node

An anti-node occurs when the displacement reaches its maximum or minimum value. The maximum value of the sine function occurs when \(\sin(\theta) = \pm 1\). So, we can set the displacement term equal to either 1 or -1 and find the position of an anti-node: \(\sin\left(\frac{\pi x}{15}\right) = 1\) or \(\sin\left(\frac{\pi x}{15}\right) = -1\) We can find the position of a nearby anti-node for both cases by taking the inverse sine: \(x = \frac{15}{\pi}\arcsin(1) = \frac{15}{\pi}\cdot\frac{\pi}{2} = 7.5\) and \(x = \frac{15}{\pi}\arcsin(-1) = \frac{15}{\pi}\cdot\frac{3\pi}{2} = 22.5\) The first anti-node is at x = 7.5 cm and the second anti-node is at x = 22.5 cm.
04

Find the distance between a node and the next anti-node

We can determine the distance between a node and the next anti-node by subtracting their positions: Distance = Anti-node position - Node position Distance = 7.5 cm - 0 cm = 7.5 cm (Using the first node and the first anti-node) Thus, the distance between a node and the next anti-node is 7.5 cm, which is Option (A).

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Key Concepts

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

Stationary Wave
A stationary wave, also called a standing wave, is a unique phenomenon that occurs when two waves of the same frequency and amplitude, traveling in opposite directions, interfere with one another. Unlike traveling waves, which carry energy from one place to another, stationary waves appear to be fixed in position. One of the most striking features of stationary waves is that they form patterns of nodes and antinodes along the medium through which they propagate.

In stationary waves, the nodes are points of no displacement, where the two interfering waves always cancel each other out. In contrast, the antinodes are points of maximum displacement, where the two waves amplify each other's effect. Understanding the formation of stationary waves and their components, nodes and antinodes, is crucial for solving related problems in physics, particularly in JEE Main Physics examinations.
Node
In the context of stationary waves, a node is a point along the medium where the wave displacement is always zero. This happens because at a node, the two interfering waves are always out of phase with each other, meaning when one wave is at a peak, the other is at a trough and they cancel each other out exactly. As a result, there is no net movement at the node, and it appears stationary.

Nodes play a critical role in identifying the characteristics of stationary waves. They are evenly spaced along the medium and can be calculated mathematically by analyzing the wave equation.
Antinode
An antinode is the polar opposite of a node in a stationary wave pattern. It's a point where the displacement of the medium reaches a maximum value. This occurs when the two interfering waves are in phase, reinforcing each other to produce a point of greatest amplitude. At antinodes, you can visually see the energy of the wave being expressed as it vibrates between its maximum and minimum values.

Recognizing antinodes is essential when studying wave phenomena, as they indicate the positions where constructive interference is taking place. The distance between adjacent nodes and antinodes provides significant information about the wave's properties.
Wave Displacement
Wave displacement refers to the amount by which a point on the wave deviates from its equilibrium position due to the energy transfer of the wave. It is a vital concept in understanding wave behavior, including the formation of stationary waves. Displacement can be either positive or negative, depending on whether the point is above or below the equilibrium position, respectively.

By examining the mathematical expression of a wave, one can determine the displacement at any point along the wave. In the given exercise, the displacement is given by a sine function, which holds the key to finding nodes and antinodes, and hence to solving problems related to stationary waves commonly found in competitive exams like the JEE Main Physics.
JEE Main Physics
The Joint Entrance Examination (JEE) Main is a competitive test in India for admission to various undergraduate engineering and architecture courses. The Physics section of JEE Main evaluates a candidate's grasp of fundamental physics concepts, including mechanics, electromagnetism, thermodynamics, optics, and waves. A solid understanding of stationary waves, nodes, antinodes, and wave displacement is imperative for aspirants, as these topics frequently appear in the exam.

Problems such as calculating the distance between nodes and antinodes challenge students to apply their theoretical knowledge to practical scenarios. Mastery of these concepts can significantly improve a student's performance in the JEE Main Physics section, assisting them in securing a seat in their desired institutes.

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Most popular questions from this chapter

Two trains \((A\) and \(B\) ) are moving towards each other on two parallel tracks at the same speed with respect to the ground. The whistle of train \(A\) blows. In which of the following cases, the frequency of the sound heard by a passenger on the other train \(B\) will be greatest? (A) If the air is still. (B) If a wind blows in the same direction and at the same speed as the other train \(B\). (C) If a wind blows in the opposite direction and at the same speed as the other train \(B\). (D) Frequency will be same in the above three cases.

Starting from the origin a body oscillates simple harmonically with a period of \(2 \mathrm{~s}\). After what time will its kinetic energy be \(75 \%\) of the total energy? (A) \(\frac{1}{6} \mathrm{~s}\) (B) \(\frac{1}{4} \mathrm{~s}\) (C) \(\frac{1}{3} \mathrm{~s}\) (D) \(\frac{1}{12} s\)

A long wire \(A B C\) is made by joining two wires \(A B\) and \(B C\) of equal area of cross-section. \(A B\) has length \(4.8 \mathrm{~m}\) and mass \(0.12 \mathrm{~kg}\) while \(B C\) has length \(2.56\) \(\mathrm{m}\) and mass \(0.4 \mathrm{~kg}\). The wire is under a tension of \(160 \mathrm{~N}\). A wave \(Y\) (in \(\mathrm{cm})=3.5 \sin (k x-w t)\) is sent along \(A B C\) from end \(A\). No power is dissipated during propagation of wave. Column-I (A) Amplitude of reflected wave (B) Amplitude of transmitted wave (C) Maximum displacement of antinodes in the wire \(A B\) (D) Percentage fraction of power transmitted in the wire \(B C\) \begin{tabular}{l} Column-II \\ \hline 1. \(2.0\) \end{tabular} \(1.5\) 2 3 . 5 \(-1\) 82 4 \(=\) 5 . 92

A body executes simple harmonic motion. The potential energy (PE), the kinetic energy (KE) and total energy (TE) are measured as a function of displacement \(x\). Which of the following statements is true ? (A) \(\mathrm{KE}\) is maximum when \(x=0\). (B) TE is zero when \(x=0\) (C) \(\mathrm{KE}\) is maximum when \(x\) is maximum (D) \(\mathrm{PE}\) is maximum when \(x=0\)

In a simple harmonic oscillator, at the mean position (A) kinetic energy is minimum, potential energy is maximum. (B) both kinetic and potential energies are maximum. (C) kinetic energy is maximum, potential energy is minimum. (D) both kinetic and potential energies are minimum.

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