Ma'anar ƙamus na "halayen bango" yana nufin ƙananan matakan radiation da ke samuwa a cikin muhalli daga yanayi na halitta da na mutum. Wannan radiation yana kasancewa koyaushe a cikin yanayi da kuma saman duniya, kuma yawanci ana auna shi a cikin raka'a na microsiverts a kowace awa (µSv/h). Abubuwan da suka samo asali daga baya sun haɗa da hasken sararin samaniya, abubuwan da ke faruwa a zahiri a cikin ɓangarorin duniya da yanayin yanayi, har ma a cikin jikinmu, yayin da tushen ɗan adam ya haɗa da hanyoyin likita, cibiyoyin makamashin nukiliya, da gwajin makamai. Ana amfani da kalmar "bayan haske" sau da yawa a cikin yanayin kare lafiyar radiation da kuma kula da muhalli.