The fact that the formula used by Hannay in the preceding Comment [J. Opt. Soc. Am. A 25, 2165 (2008)
] is “from a standard text on electrodynamics” neither warrants that it is universally applicable nor that it is unequivocally correct. We have explicitly shown [J. Opt. Soc. Am. A 25, 543 (2008)
] that, since it does not include the boundary contribution toward the value of the field, the formula in question is not applicable when the source is extended and has a distribution pattern that rotates faster than light in vacuo. The neglected boundary term in the retarded solution to the wave equation governing the electromagnetic field forms the basis of diffraction theory. If this term were identically zero, for the reasons given by Hannay, the diffraction of electromagnetic waves through apertures on a surface enclosing a source would have been impossible.
© 2008 Optical Society of America
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