Chapter 6: Optics27withI=±|±S|²it follows:R+T=1. A special case isr±=0. This happens if the angle between the reFectedand transmitted rays is90◦. ±rom Snell’s law it then follows:tan(θi)=n. This angle is calledBrewster’sangle. The situation withr⊥is not possible.6.6PolarizationThe polarization is de²ned as:P=IpIp+Iu=Imax-IminImax+Iminwhere the intensity of the polarized light is given byIpand the intensity of the unpolarized light is given byIu.ImaxandIminare the maximum and minimum intensities when the light passes a polarizer. If polarizedlight passes through a polarizerMalus lawapplies:I(θI(0) cos2(θ)whereθis the angle of the polarizer.The state of a light ray can be described by theStokes-parameters: start with 4 ²lters which each transmits halfthe intensity. The ²rst is independent of the polarization, the second and third are linear polarizers with thetransmission axes horizontal and at+45◦
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