where is the (constant) complex amplitude vector, is the imaginary unit, is the wave vector (whose magnitude is the angular wavenumber), is the position vector, is the angular frequency, is time, and it is understood that the real part of the expression is the physical field.The above form () is typically used by physicists. Electrical engineers typically prefer the form that is, they not only use instead of for the imaginary unit, but also change the sign of the exponent, with the result that the whole expression is replaced by its complex conjugate, leaving the real part unchanged . The electrical engineers' form and the formulas derived therefrom may be converted to the physicists' convention by substituting for . The value of the expression is unchanged if the position varies in a direction normal to ; hence is normal to the wavefronts.
where is the (constant) complex amplitude vector, is the imaginary unit, is the wave vector (whose magnitude is the angular wavenumber), is the position vector, is the angular frequency, is time, and it is understood that the real part of the expression is the physical field.The above form () is typically used by physicists Electrical engineers typically prefer the form that i.s, they not only use instead of for the imaginary unit, but also change the sign of the exponent, with the result that the whole expression is replaced by its complex conjugate, leaving the real part unchanged . The electrical engineers' form and the formulas derived therefrom may be converted to the physicists' convention by substituting for . The value of the expression is unchanged if the position varies in a direction normal to ; hence is normal to the wavefronts.