Phase Difference between Two Points on a Wave and Path Difference Explained - interactive


Phase difference and path difference of waves

In the above animation, five points on the wave are considered for the explanation. 

The fully interactive applet is given below for you to practise.

The phase of a point implies its direction of vibration on a wave. For example, both points A and E vibrate exactly the same way are said to be in phase: when A goes up so does B; the phase difference is either 00 or 3600.

If you consider the motion of points A and C, on the other hand, when A goes down C goes up or vice versa. Therefore, A and C are said to be out of phase; the phase difference is 1800.

That means the phase difference between two points on a wave - or two waves for that matter - can take any value between 00 and 3600

The phase difference between points A and B, for instance, is 900.

From the above examples, it is clear there is a connection between the path difference between two points - or two waves - and phase difference. It is as follows:

Phase difference = (path difference / wavelength) x 360

φ = x/λ X 3600, where x is the distance between two points or waves.

Wave Profile

The snap shot of a wave taken at a given time is called a wave profile. It is the displacement of the particles of a wave against the distance. The following image is a snap shot of the above wave - hence, a wave profile.

Wave profile

You can practise the phase difference with the following applet:


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