ðə tɹˈaɪɾiəm ɪn ɐ ɡˈæʃəs tɹˈaɪɾiəm lˈaɪt sˈoːɹs ˌʌndɚɡˈoʊz bˈeɪɾə dᵻkˈeɪ, ɹᵻlˈiːsɪŋ ᵻlˈɛktɹɑːnz wˌɪtʃ kˈɔːz ðə fˈɑːsfɚ lˈeɪɚ tə flˈʊɹɹɛs.
The tritium in a gaseous tritium light source undergoes beta decay, releasing electrons which cause the phosphor layer to fluoresce.