Poynting Vector
One main feature of an electromagnetic wave is that it can transport energy from point to point. the rate of energy flow per unit area in a plane electromagnetic wave is defined by a vector 
called the Poynting vector.
Or, the unit of S is W/m2, the direction of S gives the direction in which the energy is transferred. 
and 
refer to instantaneous values at the point under consideration.
Services: - Poynting Vector Homework | Poynting Vector Homework Help | Poynting Vector Homework Help Services | Live Poynting Vector Homework Help | Poynting Vector Homework Tutors | Online Poynting Vector Homework Help | Poynting Vector Tutors | Online Poynting Vector Tutors | Poynting Vector Homework Services | Poynting Vector