The Energy Density of an Electromagnetic Wave in Free Space

Multiple Choice

The energy density of an electromagnetic wave in free space is

A) 1/4 in the electric field and 3/4 in the magnetic field.
B) equally divided between the magnetic and the electric fields.
C) entirely in the magnetic field.
D) entirely in the electric field.
E) 1/4 in the magnetic field and 3/4 in the electric field.