To explain polarisation, my book gives an example of a transverse wave in a string, and explains as:

Since each point on the string moves on a straight line, the wave is also referred to as a linearly polarised wave. Further, the string always remains confined to the x-y plane and therefore it is also referred to as a plane polarised wave

The image given is somewhat like this: enter image description here

The definitions for both these terms are different, so it seems to me that they are not same. But I wasn't able to find an example which illustrates the difference between these two.

I found this Quora question, but the answers don't seem convincing.

So what exactly is the difference between a linearly polarised wave and a plane-polarised wave? Because according to me, a linearly polarised wave will oscillate in only one plane.

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    $\begingroup$ I've always taken them as synonymous. The main distinction is between plane [linear] and circularly polarized light, which doesn't oscillate in any one plane. $\endgroup$ Feb 22, 2019 at 21:22
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    $\begingroup$ linear polarisation only talks about direction of oscillation of electric field for example y polarised light has it electric field amplitude only in y-direction and it direction propogation is not specified . we need plane of polarisation to specify a waves oscillation as well as direction of propogation. y polarised light can propogate in x-direction or in z- direction. this distinction (linear polarisation and plane polarisation ) is required to know direction of oscillation as well as direction of propogation $\endgroup$
    – teja
    Jun 3, 2019 at 6:06

2 Answers 2


Linearly polarized wave is same as plane polarized wave. Why we call it linearly polarized ? Because oscillation taking place along a line. Why we call it plane polarized ? Since oscillation taking place along one axis & the wave is forward in motion along another axis. Two axes are used , so called plane.


Linearly polarized wave Oscillate in a single plane and the magnitude of electric field vector varies sinusoidally as a function of time.

Circularly polarized wave have their magnitude of electric field vector constant, but their phase change periodically as a function of time.(i.e. the electric field vector rotate periodically as a function of time)

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    $\begingroup$ In your answer, shouldn't it be displacement(or something else) varies sinusoidally as a function of time instead of amplitude varies sinusoidally as a function of time $\endgroup$
    – Eagle
    Feb 23, 2019 at 12:03
  • $\begingroup$ I'm sorry. I had written amplitude instead of writing electric field vector. $\endgroup$
    – walber97
    Feb 24, 2019 at 6:37

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