Which one of the following is the incorrect statement regarding Poyting vector?

Concept:

Poynting vector

When an electromagnetic wave propagates the electromagnetic energy flows in a direction of vector\(\left ( \vec{E} \times \vec{H}\right )\), the total energy flowing perpendicular per unit time per unit area is called "Poynting vector".

Poynting vector represents the direction of energy-flux density in an electromagnetic wave propagating in a given medium.

It is represented by

  \(\vec{S}=\frac{\left ( \vec{E} \times \vec{B}\right )}{\mu _{0}}\)

Where,

  \(\vec{S}\)= Poynting vector

  \(\vec{E}\)= Electric field vector

  \(\vec{B}\)= Magnetic field vector

  \(\mu _{0}\)= Permeability of free space

Explanation:

Statement 1: According to the definition of the Poynting vector, It represents the total energy flowing through electromagnetic waves perpendicular per unit time per unit area.

The unit Poynting vector same unit as the Intensity of the wave.

The SI unit of the Poynting vector is Watt/m².

Hence, Statement 1 is correct.

Statement 2:The direction of the Poynting vector is mutually perpendicular to the electric and magnetic field components.

Statement 3:The maximum value of the Poynting vector will be zero.

The magnitude of the Poynting vector is also called the intensity of the electromagnetic waves.

       i.e, \(S=\frac{EBsin\theta }{\mu _{0}}\)

 Where,

•  \(\theta\) is the angle between \(\vec{E}\)and\(\vec{B}\).
• The Poynting vector of an electromagnetic wave is time-dependent, i.e, its magnitude varies with time.
• When the angle between\(\vec{E}\) and\(\vec{B}\) is\(\pi/2\), then \(\vec{S}\)is maximum with the value of\(S=\frac{EB }{\mu _{0}}\).

Hence, Option-3 is correct.