Photovoltaic modules play an important role in producing electrical energy on environmentally friendly way. To ensure it's best performance, we have to properly protect them against external circumstances. One way is to use encapsulating materials. These materials affect the light in way that it reduces light flow. That is why it is important to know it's optical properties.
Within this thesis we determined refractive indices of glass and different encapsulating foils. We determined them by measuring reflection and transmission and by using appropriate numerical tool. In the end we compared results.