When E and B Are the Amplitudes of the Electric $\frac { 1 } { 4 } \varepsilon _ { 0 } E ^ { 2 }$

Multiple Choice

When E and B are the amplitudes of the electric and magnetic fields in an electromagnetic wave in vacuum,the total average energy density in the wave is

A) $\frac { 1 } { 4 } \varepsilon _ { 0 } E ^ { 2 }$ .
B) $\frac { 1 } { 2 } \varepsilon _ { 0 } E ^ { 2 }$ .
C) $\varepsilon$ ₀E².
D) $\frac { B ^ { 2 } } { \mu _ { 0 } }$ .
E) $\frac { E B } { \mu _ { 0 } }$ .