Tiān-chû-pho

Tiān-chû-pho (electromagnetic wave) sī ū tiān-tiûⁿ (electric field) ham chû-tiûⁿ (magnetic field) tī khong-kan thoân-pò ê 1 chióng pho. Tiān-chû-pho sī tiān-chû hok-siā hiān-siōng ê chi̍t bīn; lán pêng-sò͘ kóng ê kng, khêng-si̍t tō sī tiān-chû-pho. Tiān-tiûⁿ ham chû-tiûⁿ chiâⁿ-chò 90° teh hàiⁿ-tāng (oscillate), kap thoân-pò ê hong-hiòng mā lóng sio khiā-ti̍t.

Tiān-chû-pho ū lêng-liōng ham ūn-tōng-liōng, ē-tàng thoân hō͘ tú--tio̍h ê bu̍t-chit.