10.6: Example- Copper
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- 22725
The real and imaginary parts \(\left(\mathrm{n}_{\theta}+i \kappa_{\theta}\right)=\sqrt{\epsilon_{\mathrm{r}}-\sin ^{2} \theta}\) have been plotted in Figure (10.6.8) as a function of the angle of incidence, θ, for room temperature copper and for a wavelength of λ= 0.5145 microns (see Table(10.1)). As can be seen from the figure, the angular dependence of the indices nθ, \(\kappa\)θ is not very pronounced. For a lossy material such as copper that has a complex dielectric constant the reflectivity, ER/E0, is complex; that is, the phase shift between the incident wave and reflected wave electric vectors is neither 0◦ (in phase) nor 180◦ (out of phase). The real and imaginary parts of the reflectivity have been plotted in Figure (10.6.9) as a function of the angle of incidence for S-polarized 0.5145 micron light incident on room temperature copper; the absolute value of the reflectivity has been plotted in Figure (10.6.10).
Similarly, the real and the imaginary parts of the ratio HR/H0 have been plotted in Figure (10.6.11) as a function of the angle of incidence for P-polarized 0.5145 micron light incident on copper; the absolute value of this ratio is shown in Figure (10.6.12). The reflection coefficient for P-polarized radiation is given by RP = ER/E0 but this is very closely related to the ratio HR/H0 because E0 = Z0H0 and ER = −Z0HR, where Z0= 377 Ohms, the impedance of free space. Notice that the real part of the reflectivity for P-polarized light vanishes at an angle of incidence of approximately 69◦ ; the phase of the reflected light at that angle is shifted by 90◦ relative to the incident light. The phase shift between reflected and incident light is much less pronounced for S-polarized light; approximately 15◦ for an angle of incidence of 69◦ .