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# Physik MFT/MI FH HN K, Rauschnabel               12/98    #
# Fresnelsche Formeln                                       #
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set dummy alpha
set grid
set title "Fresnelsche Formeln"
set xlabel "Einfallswinkel alpha" 
set xrange [0 : 90]
set ylabel "Refl. Koeff.  r"
set yrange [-1.05:1.05]
set ytics -1,0.1
#
n1 = 1.0
n2 = 1.5
#
deg2rad = pi/180.
beta(alpha)=asin(sin(alpha)*n1/n2)
r_par(alpha) = -tan(alpha-beta(alpha))/tan(alpha+beta(alpha))
r_senkr(alpha) = - sin(alpha-beta(alpha))/sin(alpha+beta(alpha))
#
a_brew = atan(n2/n1) / deg2rad
set arrow 1 from a_brew,0.4 to a_brew,0
set label 1 "Brewster-Winkel" at a_brew,0.45 center 
#
set key 30,0.9
plot 0 notit, r_par( alpha*deg2rad ) , r_senkr( alpha*deg2rad )
#