# CBSE Class 11 Physics Notes Chapter 14 Oscillations

## What are Oscillations?

Oscillation is a measure of some repetitive variation, as a function of time. It can be measured with respect to a state of equilibrium. The most common and simplest example for oscillation is the motion of a simple pendulum.

### What are the three main types of Simple Harmonic Motion?

The three main types of simple harmonic motion in physics are:

• Free Oscillation
• Forced Oscillation
• Damped Oscillations

### Free Oscillation

In here, the amplitude and time period remains constant without any influence of external factors. When the system has zero damping, the amplitude remains constant provided, this theory is possible in cases where damping always occurs.

In order to overcome external forces like air resistance or friction, the reduction in amplitude(energy loss of a system) is referred to as damping. As a result, the amplitude, frequency, and energy all remain constant.

### Forced Oscillation

When an external periodic force influences a body’s oscillation, then it is called forced oscillation. Here, damping occurs in the amplitude of oscillation but remains constant with the help of the external energy supplied by the system.

For example, constantly pushing a swing so that its oscillation doesn’t reduce.

### Damped Oscillation

The reduction of the amplitude of an object with respect to time, such type of oscillations are known as damped oscillations. The energy of a system decreases with the decrease in amplitude. There are two types of damping:

• Natural Damping
• Artificial Damping

See more on the same:Â Free Forced And Damped Oscillations

### Resonance

It is the phenomenon wherein an external vibrating system causes the oscillation of another system with a higher amplitude at a particular frequency. The frequency at that particular resonance level is known as a resonant frequency. For instance, when tuning a guitar with the help of another guitar, the resonant frequency can be observed. In this case, the amplitude of the vibration of the string is the highest. The reason for large amplitude oscillations generated at that resonant frequencies are as a result of vibrational energy that is accumulated in the system. Resonance is of the following types:

• Mechanical
• Acoustic
• Orbital
• Particle
• Electrical
• Optical Resonance

### Important Questions

1. Which of the following examples represent periodic motion?
• (a)The return trip of a swimmer when he is completing one trip from the bank of a river to the other
• (b)The release of a freely hanging bar magnet which has been displaced in N-S direction
• (c)Rotating a hydrogen molecule about its mass’s center
• (d)The release of an arrow from a bow
1. Which of the following examples represent (nearly) simple harmonic motion and which represent periodic but not simple harmonic motion?
• (a)Earth’s rotation on its axis
• (b)In U-tube, the oscillating motion of the mercury column
• (c)When a smoothly curved ball is released from the point which is above the lowermost point, the motion of the ball bearing inside of the ball
• (d)In a polyatomic molecule, the general vibrations about its equilibrium

This was about CBSE Physics Chapter 14 Oscillations. Stay tuned with BYJU’S for more.

## Frequently asked Questions on CBSE Class 11 Physics Notes Chapter 14: Oscillations

### What is meaning of â€˜oscillatory motionâ€™?

A motion repeating itself is referred to as periodic or oscillatory motion.

### What is â€˜resonanceâ€™?

Resonance describes the phenomenon of increased amplitude that occurs when the frequency of a periodically applied force is equal or close to a natural frequency of the system on which it acts.

### What is â€˜acoustic soundâ€™?

Acoustics is the science related to the production, control, transmission, reception and effects of sound.