試題詳解

47. For a classical electromagnetic plane wave travelling in the x direction in a vacuum (with speed c), the electric field has the form = E₀ cos(kx - wt) (V/m). Which of the following statements is true?
(A) The magnetic field oscillates in the x direction with an amplitude | E₀l/c (T).
(B) The energy density of the electromagnetic wave is a constant everywhere in space.
(C) The radiation pressure due to the electromagnetic wave shinning on a wall does not depend on its frequency.
(D) The instantons power per unit area delivered by the electromagnetic wave is a constant.
(E) None of the above is correct.