Board Thread:Off Topic/@comment-26397825-20151211051732/@comment-24891101-20151222071820

Really, given that in the trans-white-body regime it almost turns an arbitrary space into a gain medium, past 100% it'll be at least exponential of exponential, so as not to utterly fry everything between two parallel surfaces. Under 0%, it's far less of an issue because there's no amplification due to reflection; it's a flat multiplicative factor of incident radiation.