s ▁principle ▁is ▁the ▁ext inction ▁par ado x , ▁which ▁states ▁that ▁in ▁the ▁diff raction ▁limit , ▁the ▁radiation ▁removed ▁from ▁the ▁beam ▁due ▁to ▁a ▁particle ▁is ▁equal ▁to ▁twice ▁the ▁particle ' s ▁cross ▁section ▁times ▁the ▁flux . ▁This ▁is ▁because ▁the ▁amount ▁of ▁radiation ▁absor bed ▁or ▁reflected ▁is ▁equal ▁to ▁the ▁flux ▁through ▁the ▁particle ' s ▁cross - section , ▁but ▁by ▁Bab inet ' s ▁principle ▁the ▁light ▁diff ract ed ▁forward ▁is ▁the ▁same ▁as ▁the ▁light ▁that ▁would ▁pass ▁through ▁a ▁hole ▁in ▁the ▁shape ▁of ▁a ▁particle ; ▁so ▁amount ▁of ▁the ▁light ▁diff ract ed ▁forward ▁also ▁equals ▁the ▁flux ▁through ▁the ▁particle ' s ▁cross ▁section . ▁ ▁The ▁principle ▁is ▁most ▁often ▁used ▁in ▁opt ics ▁but ▁it ▁is ▁also ▁true ▁for ▁other ▁forms ▁of ▁elect romagnet ic ▁radiation ▁and ▁is , ▁in ▁fact , ▁a ▁general ▁theorem ▁of ▁diff raction ▁in ▁wave ▁mechan ics . ▁Bab inet ' s ▁principle ▁finds ▁most ▁use ▁in ▁its ▁ability ▁to ▁detect ▁equivalence ▁in ▁size ▁and ▁shape . ▁ ▁Dem on str ation ▁experiment ▁The ▁effect ▁can ▁be ▁simply ▁observed ▁by ▁using ▁a ▁las er . ▁First ▁place ▁a ▁thin ▁( approx . ▁ 0 . 1   mm ) ▁wire ▁into ▁the ▁las er ▁beam ▁and ▁observe ▁the ▁diff raction ▁pattern . ▁Then ▁observe ▁the ▁diff raction ▁pattern ▁when ▁the ▁las er ▁is ▁sh one ▁through ▁a ▁narrow ▁sl it . ▁The ▁sl it ▁can ▁be ▁made ▁either ▁by ▁using