In an electromagnetic wave, the amplitude of electric firld is `1 V/m`. The frequency of wave is `5xx10^(14)Hz`. The wave is propagating along `z`-axis. The average energy density of electric field, in `"joule"//m^(3)`,will be

Explanation

Average energy density is given by
`U_(E)=`
`1/2 varepsilon_(0)E^(2)=1/2 varepsilon_(0) (E_(o)/sqrt(2))^(2)=1/4 varepsilon_(o)E_(o)^(2)= 1/4xx8.85x10^(-12)`
`xx(1)^(2)=2.2xx10^(-12)J//m^(2)`