Komai na gaba ko na baya hazo fitilun, ƙa'idar a zahiri iri ɗaya ce. Don haka me yasa hazo na gaba da baya suke launuka daban-daban? Wannan shine yadda ake dacewa da yanayin gida. A mafi yawan lokuta, raya hazo fitilu ja ne, don haka me ya sa ba farin raya hazo fitilu? Tun da an riga an “majagaba” fitilun baya, an yi amfani da ja a matsayin tushen hasken don guje wa yin kuskure. Kodayake hasken yana kama da fitilun birki. A gaskiya ma, ƙa'idar ba ɗaya ba ce kamar yadda tasirin ba ɗaya ba ne, a cikin yanayin rashin gani sosai ya kamata ya buɗe fitilun hazo don ƙarin haske. A saukaka wa motocin da ke zuwa daga baya don ganowa.
