This window helps calculating the amount of light reflected and transmitted through a vacuum-glass interface. 

In the first section the index of refraction of the glass has to be specified. 
The index can be entered directly, via its Brewster angle or chossing a glass and a wavelengh. 
The glass types BK7, fused silica, F2, SF10 and SF11 are available. 
The relation between Brewster's angle and refractive index is: 

• index = tan(brewster_angle)

In the second section either the angle of incidence or the angle of refraction on the glass surface has to be entered. 
The relation between the two angles is given by Snell's law: 

• sin(angle_in_vacuum)=index*sin(angle_in_glass)

The third section displays the relative intensity reflected from and transmitted through the vacuum-glass interface. 
These values depend on the polarization and are given for p- and for s-polarized light: 

• p-reflection = (index*cos(angle_in_vacuum)-cos(angle_in_glass)^2/(index*cos(angle_in_vacuum)+cos(angle_in_glass))^2 
• s-reflection = (cos(angle_in_vacuum)-index*cos(angle_in_glass)^2/(cos(angle_in_vacuum)+index*cos(angle_in_glass))^2
• transmission = 1-reflection