The present paper describes reflection and transmission of a plane electromagnetic wave by a dielectric half‐space which is moving uniformly perpendicular to the plane of incidence. It is found that for the incidentEplane wave both the reflected and transmitted waves are no longer anEplane wave but a linear combination ofEandHplane waves. In addition, it is shown that for the incidentEwave theE‐wave components of the reflected and transmitted waves carry a positive power, but the power flow with regard to theH‐wave component of the transmitted wave is always negative while the power carried by theH‐wave component of the reflected wave is always positive.