# What is the average energy density ⟨ue⟩ in the electric field of the wave?

Jul 24, 2022

In classical electrodynamics, the average energy density in an electromagnetic field is given by the Poynting vector. In a uniform plane wave, the time-averaged Poynting vector is perpendicular to the direction of propagation and is given by:

⟨ue⟩=1/2⟨E⋅B⟩

where ⟨E⋅B⟩ is the time-averaged value of the dot product of the electric and magnetic fields. The SI unit of energy density is joules per cubic meter (J/m3).

In a plane wave, the electric and magnetic fields are perpendicular to each other and to the direction of propagation. The energy density is therefore:

⟨ue⟩=1/2⟨E⋅B⟩=1/2⟨E⋅H⟩

where H is the magnetic field intensity. The SI unit of energy density is joules per cubic meter (J/m3).

## Other related questions:

### Q: What is the average energy density in the electric field of the wave?

A: The electric field of the wave has an average energy density of E^2/8pi

### Q: What is the formula of energy density of wave?

A: The energy density of a wave is given by:

energy density = wave amplitude squared / (2 * wave speed)

### Q: How do you calculate electric energy density?

A: The electric energy density is given by:

energy density = 1/2 * ε * E^2

where ε is the permittivity of the medium and E is the electric field strength.

### Q: Which is the energy density of a magnetic field?

A: The energy density of a magnetic field is given by:

E = B^2/(2mu_0)

where B is the magnetic field strength and mu_0 is the permeability of free space.