More exactly, below. (Lower frequency, outside the visible interval with ultra-violet at the other end.)
As in 'infra-dig' meaning something being 'beneath dignity' to be done, https://en.wiktionary.org/wiki/infra_dig
More exactly, below. (Lower frequency, outside the visible interval with ultra-violet at the other end.)
As in 'infra-dig' meaning something being 'beneath dignity' to be done, https://en.wiktionary.org/wiki/infra_dig