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# Oscillations and Waves: JEE Main Physics

Oscillations are repetitive variations in a system’s physical quantities about a central value or between two or more different states. These can be seen in various physical systems, such as the swinging of a pendulum, the vibration of a guitar string, or the alternating current in electrical circuits.

## Simple Harmonic Motion (SHM)

The simplest type of oscillation is Simple Harmonic Motion (SHM). It can be described as periodic motion in which the restoring force is directly proportional to the displacement and acts in the direction opposite to that of displacement.

### Mathematical Representation of SHM:

where:

• ( x(t) ) is the displacement at time ( t ),
• ( A ) is the amplitude of oscillation,
• ( /ω ) is the angular frequency,
• ( \ϕ ) is the phase constant.

## Angular Frequency and Period

The angular frequency ( \ω ) is related to the frequency ( f ) and the period ( T ) of the oscillation as:

where:

• ( f ) is the number of oscillations per unit time,
• ( T ) is the time taken for one complete oscillation.

## Energy in SHM

The total mechanical energy in SHM is the sum of its potential energy (PE) and kinetic energy (KE). It remains constant if there is no damping force.

## Damped and Forced Oscillations

• Damped Oscillations: These occur when a resistive force (such as friction) acts on the oscillating system, causing the amplitude to gradually decrease over time.
• Forced Oscillations: When an external periodic force drives the system, it leads to forced oscillations. If the frequency of this force matches the natural frequency of the system, resonance occurs, causing a significant increase in amplitude.

## Waves

A wave is a disturbance that propagates through a medium, transferring energy from one point to another without the transport of matter.

### Types of Waves:

1. Mechanical Waves: Require a medium to propagate, e.g., sound waves.
2. Electromagnetic Waves: Do not require a medium, e.g., light waves.

### Characteristics of Waves:

• Wavelength ((\lambda)): The distance between successive crests or troughs.
• Frequency (f): The number of waves passing a point per second.
• Velocity (v): The speed at which the wave propagates through the medium, given by ( v = f \λ ).

### Wave Equation

For a wave traveling in one dimension, the wave equation is:

## Superposition Principle

When two or more waves overlap, the resultant displacement at any point is the algebraic sum of the displacements due to each wave. This principle is known as the superposition principle.

## Interference and Beats

• Interference: The phenomenon where two waves superpose to form a resultant wave of greater, lower, or the same amplitude.
• Constructive Interference: Occurs when waves combine to make a wave with larger amplitude.
• Destructive Interference: Occurs when waves combine to make a wave with smaller amplitude.
• Beats: When two waves of slightly different frequencies interfere, the resultant wave fluctuates in amplitude, producing beats. The beat frequency is given by:

### Standing Waves

Standing waves are formed by the superposition of two waves traveling in opposite directions with the same frequency and amplitude. Nodes (points of zero amplitude) and antinodes (points of maximum amplitude) are characteristic features of standing waves.

### Fundamental Frequency and Harmonics:

• Fundamental Frequency: The lowest frequency at which a system oscillates.
• Harmonics: Integer multiples of the fundamental frequency.

## Conclusion

Understanding oscillations and waves is crucial for various applications in physics, engineering, and other sciences. From musical instruments to communication systems, the principles of oscillatory motion and wave propagation are foundational to technology and nature.

## JEE Advanced Previous Year Paper

JEE Advanced: 28-Aug-2022  ( Shift 1 )

JEE Advanced: 4-Jun-2023 ( Shift 2 )

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