Show that the avearge energy density of the electric field `vecE` equals the average energy density of the magnetic field `vecB`, in electromagnetic waves.

Explanation

Average energy density of `E`
`U_(E) = (1)/(4) epsilon_(0) E_(0)^(2)`
Average energy density of B
`U_(B) = (1)/(4) (B_(0)^(2))/(mu_(0))`
`because c = (E_0)/(B_0)` So.
`U_(E) = (1)/(4) epsilon_(0) (c B_(0))^(2) = (1)/(4) epsilon_(0) c^(2) B_(0)^(2) = (1)/(4) epsilon_(0) (1)/((mu_(0) epsilon_(0))) xx B_(0)^(2)`
`= (1)/(4) (B_(0)^(2))/(mu_(0))`
`U_(E) = U_(B)`