1. (a) Show that the dispersion relationship for the dielectric constant at low density of atoms is given by: Ne? 4,(W)=

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1 A Show That The Dispersion Relationship For The Dielectric Constant At Low Density Of Atoms Is Given By Ne 4 W 1 (67.09 KiB) Viewed 19 times

1. (a) Show that the dispersion relationship for the dielectric constant at low density of atoms is given by: Ne? 4,(W)=1+2+ 6** (003 - 02° +1 [6 marks (b) How does this expression change when multiple resonances are taken into account? [3 marks (c) At a high density of atoms, the Clausius-Mosotti equation will apply. Derive this equation given that the field due to the other dipoles Es is: E 36 [4 marks 1. (d) Explain how reflection and absorption spectra can be calculated once the dispersion of the dielectric constant is known. [4 marks (e) The data shown in the figure below is the refractive index (n) and extinction coefficient (K) for ZnSe. The full lines are from theory and the points are the experimental measurements. Explain the main features of these spectra. [4 marks) (m) Estimate (a) the bandgap of ZnSe and (b) the transmitivity of the sample at 1 eV [4 marks] 35 30- 25 2001 nik 1.5 - ZnSe 1.우 0.5 0 0 1 1 2 3 . 4 5 (ev) 6 7 اليا