Once again, the terms become very small very quickly. Because even the largest internal-reflection induced term (<math> 2 C _2 C _3 </math>) is more than an order of magnitude smaller than the needed terms, we can treat all internal reflection as error and ignore it. | Once again, the terms become very small very quickly. Because even the largest internal-reflection induced term (<math> 2 C _2 C _3 </math>) is more than an order of magnitude smaller than the needed terms, we can treat all internal reflection as error and ignore it. |