Thick lens: matrix method the matrix can be expanded 1 as 0 1 0 1 1 m = r n' r2 t 0 and the lens is surrounded by the same medium, . for a thin lens t is negligible, n n'. 1 0 1 m = r2 n 1 multiplying yields 1 1 m = ry r o ancdeskiops example 1: find the system matrix for the think lens shown below given that ri 45 cm, r2 30 cm, t = 5 cm, n, 1.6, and n = n' 1. yo