Anyway, My question is whether exact form of Group velocity is [tex]\frac{dw}{dk}[/tex]

or [tex]\frac{dw}{dk}|_{\bar{k}}[/tex]

I want to know whether Group velocity is independent of K, propagation number

Becasue Group velocity is 'proper' speed of generally complex wave in comparision with

phase velocity So These exists only one Group velocity of certain wave which should not be

dependent of any K

Second Question is what does Group delay means? I have to drive Formula of Group delay

,[tex]\frac{d\varphi }{dw}[/tex] but i don't know what does it means.

Please Solve my question.