With a polycarbonate (PC)-poly(methyl methacrylate) (PMMA) graft copolymer and a PC-poly(dimethyl siloxane) (PDMS) block copolymer, the relationship between the composition of PC copolymers and the refractive index (n(D)) was investigated. According to the results. with a PMMA content of 38 wt %, the n(D) value of the PC-PMMA graft copolymer was nearly the same as that of electrical (E) glass (n(D) = 1.545), and with a PMMA content of 6 wt %, it was nearly the same as that of electrical corrosion resistance (ECR) glass (n(D) = 1.579). However, with a PDMS content of 19 wt the n(D) value of the PC-PDMS block copolymer was nearly the same as that of E glass, and with a PDMS content of 2 wt it was nearly the same as that of ECR glass. The combination of the PC-PDMS block copolymer and the glass fibers (GFs) of ECR glass led to haze values of 8 and 16% with GF contents of 10 and 20% respectively.