image (67)

where ξ*image is a real number. To understand the meaning of Eq. (67), let us substitute it into the general expression Eq. (34); we get

uz(x,y,t)=h(y)ei(ξxωt)=h(y)ei(iξ*x)eiωt (68)

image (68)


uz(x,y,t)=[h(y)eξ*x]eiωt (69)

image (69)

Equation (69) describes an evanescent1 wave, which has a decaying amplitude and only exists close to the excitation ...

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