Ukuba luntwentwe

Emkhakheni womchazakhanyo (optics) , ukuba luntwentwe noma ubuncwamanzi isakhi esingokoqobo sokuvumela ukukhanya ukuba kudlule maphakathi nento ngaphandle kokusakazeka kwabo. Emlinganisweni omkhulu (lapho imiyinge imikhulu kunamabangacuphi amabane ahilelekile), amabane kungashiwo kuthiwe alandela umthetho ka-Snell. Ukuba luntwentwebi? (Translucency) nakho kuvumela ukukhanya kudlule, kodwa akuwulandeli umthetho ka-Snell emlinganisweni omkhulu; amabane angasakazeka kunoma yiziphi izixhakasimo (interfaces) ezimbili, noma ngaphakathi, lapho kuba nenguquko ekugwincizeni. Ngamanye amazwi, into eluntwentwebi yakhiwa izigcoyi ezinokugwinciza okufanayo. Izinto eziluntwentwe zibonakala zicacile, zincwamanzi, zibonisa konke ukukhanya. Isakhi esilungene nokuba luntwentwebi  sibizwa imfiphalo (opacity).