Owen Duffy wrote:
"Richard "over a prolonged period" is a qualification, and still doesn`t
sufficiently qualify the statement to be true."

Maybe not the best words, but they are true in the practical case. In an
EM-wave, energy is being passed back and forth netween the electric and
magnetic fields on a periodic basis. At any given instant most of the
wave`s energy may reside mostly in one field or the other at a given
point. Half a cycle nas no practical significance among a million or
more.

Best regards, Richard Harrison, KB5WZI