Tiān-chû hòng-siā (Eng-gí: electromagnetic radiation) sī hòng-siā-sèng ê lêng-liōng, keng-kòe it-tēng ê tiân-chû kòe-têng sek-hòng.

Tiān-chû-pho sī piáu-tat tiān-chû hòng-siā hiān-siōng ê chi̍t khoán hong-sek.