# Questions tagged [poynting-vector]

The directional energy flux of an electromagnetic field. In conjunction with Poynting's theorem and the continuity equation, it used to express the conservation of electromagnetic energy, and to calculate the power flow in electric and magnetic fields.

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### Intensity of a gaussian beam

Let's say a gaussian beam propagates along z-axis. According to Wikipedia its intensity will be: $I(r,z) = I_0 \frac{\omega_0}{\omega(z)}\exp(\frac{-2r^2}{\omega(z)^2})$ I think of the intensity as a ...
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### Role of Maxwell's stress tensor in the conservation of momentum of an EM wave

Defining the Wave: Let's assume an electromagnetic wave exists in the form $\vec{E}(x,y,z,t) = \vec{E}_0 \, cos(kx-\omega t)$ $\vec{B}(x,y,z,t) = \vec{B}_0 \, cos(kx-\omega t)$ How the wave interacts ...
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### Why the intensity of a wave is $\Psi \Psi^*$?

In here at the bottom, it says the intensity of a wave is the wave phasor times it's conjucate $$I(x) = \Psi \Psi^* = |\Psi |^2$$ But when I compute the intensity of an electromagnetic wave in c.g.s, ...
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### Does a lightbulb glow due to the interaction with electromagnetic waves or due to the interaction between its atoms and the moving electrons?

Today I learned that energy is transferred to a lightbulb through electromagnetic waves produced by the movement of electrons and according to Poynting's law, the direction of this energy is ...
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### Radiation of rotating spherical shell with constant angular speed

I know this has been asked twice here but none of the explanations made me realize why it is zero. One of the answers says dipole moment for constant angular velocity is also a constant vector and ...
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### Is slower light darker?

Consider for example, electromagnetic waves inside conductors. The speed at which an EM wave travels at can be a considerable fraction lower than C So my question is, If I were standing with my eyes ...
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### Electric field strength $d$km from a television transmitter of power $P$kW, assuming isotropic radiation

I think I need to use the Poynting vector to do this, as it is equal to the power per unit area flowing through a surface. At a distance $d$km from the transmitter, the surface will have a surface ...
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### How does a Poyinting vector act on a neutron?

How does a Poyinting vector act on a neutron? As I understood a photon action on a charged particle this action is purely electromagnetic where the electric component shake the particle perpendicular ...
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