▁light ▁to ▁be ▁lost . ▁Research ers ▁mentioned ▁that ▁since ▁the ▁approach ▁can ▁be ▁scale d ▁down ▁further ▁in ▁size , ▁it ▁was ▁a ▁major ▁step ▁towards ▁a ▁clo ak ▁that ▁would ▁work ▁for ▁visible ▁light . ▁ ▁Problem s ▁of ▁ref raction ▁and ▁opacity ▁The ▁head lined ▁claims ▁that ▁labor atory ▁results ▁with ▁met am aterial s ▁are ▁demonstr ations ▁of ▁prototype ▁in visibility ▁clo aks ▁conflicts ▁with ▁two ▁facts ▁resulting ▁from ▁fundamental ▁characteristics ▁of ▁the ▁underlying ▁met am aterial ▁technology : ▁ ▁These ▁materials ▁are , ▁by ▁nature , ▁highly ▁dispers ive , ▁hence ▁light ▁passing ▁around ▁a ▁" clo aked " ▁object ▁would ▁be ▁strongly ▁ref ract ed ▁( pr isms ▁are ▁not ▁invisible ). ▁ ▁Currently ▁light ▁passing ▁through ▁these ▁materials ▁is ▁partially ▁absor bed , ▁making ▁the ▁shield ▁partially ▁ ▁op aque . ▁ ▁Per fect ▁clo aking ▁by ▁materials ▁may ▁be ▁problem atic , ▁when ▁taking ▁caus ality ▁into ▁account . ▁ ▁Ac oust ic ▁clo aking ▁ ▁Though ▁perfect ▁clo aking ▁based ▁on ▁invisible ▁paint ▁is ▁impossible ▁if ▁detect ors ▁( such ▁as ▁micro ph ones ) ▁and ▁sources ▁( such ▁as ▁loud spe akers ) ▁are ▁placed ▁round ▁a ▁volume ▁and ▁if ▁a ▁particular ▁formula ▁is ▁used ▁to ▁calculate ▁the ▁signals ▁to ▁be ▁fed ▁to ▁the ▁sources , ▁perfect ▁clo aking ▁is ▁possible . ▁Such ▁perfect ▁clo aking ▁does ▁require ▁that ▁the ▁information ▁can ▁flow ▁through ▁the ▁volume ▁fast ▁enough ▁and ▁the ▁calculations ▁can ▁be ▁performed ▁fast ▁enough ▁so ▁that ▁the ▁necessary ▁information ▁can ▁get