**Simple harmonic waves:**

A motion which repeats itself after a definite interval of time is called periodic motion. The time interval after which the motion repeats is called the time period.To know more about Simple Harmonic Waves , watch Simple Harmonic Waves Video to learn more .

**Circular motion:**

Circular motion is one example of periodic motion which we come across everyday like the hands of a clock undergo circular motion with different time periods. Similarly, if a body moves to and fro on the same path, it is said to perform oscillations. Simple harmonic motion is a type of oscillatory motion in which the displacement x of the particle from the origin is given by

x = Asin(ωt +ф)

where A, ω and ф are constants. This kind of motion where displacement is a sinusoidal function of time is called simple harmonic motion. The quantities A, ω and ф.

**Amplitude**

The quantity A is called the amplitude of the motion. As sin(ωt +ф) can take values between -1 and +1, the displacement x can take values between –A and +A. This gives the physical significance of the constant A. It is the maximum displacement of the particle from the center of oscillation i.e. the amplitude of oscillation.

**Phase Angle (ф)**

The time varying quantity (ωt +ф) is called the phase of the motion and the quantity ф is called the phase angle or phase constant. It depends on the choice of the instant t = 0. To describe the motion quantitatively, a particular instant should be called zero and measurement of time should be made from this instant. If we choose to call the instant when the particle is passing through its mean position as the time t = 0, then ф = 0 as at that time x has to be zero. But on the other hand, if for the convenience of the problem, t = 0 has to be considered at a point when the particle at an extreme position, then ф would be ±п/2 depending on the direction of velocity of the particle at that position.

Useful for CBSE, ICSE, NCERT & International Students

Grade : 9

Subject : Physics

Lesson : Wave Motion and Sound

Topic: Simple Harmonic Waves Video

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