▁a ▁las er ▁printer ▁or ▁phot oc op ier ▁to ▁print ▁onto ▁clear ▁pl astic ▁film ▁or ▁by ▁using ▁a ▁pin ▁to ▁draw ▁a ▁line ▁on ▁a ▁piece ▁of ▁glass ▁that ▁has ▁been ▁sm oked ▁over ▁a ▁cand le ▁fl ame . ▁ ▁Bab inet ' s ▁principle ▁in ▁radio fre quency ▁structures ▁Bab inet ' s ▁principle ▁can ▁be ▁used ▁in ▁anten na ▁engineering ▁to ▁find ▁complement ary ▁imped ances . ▁A ▁consequence ▁of ▁the ▁principle ▁states ▁that : ▁ ▁where ▁Z met al ▁and ▁Z sl ot ▁are ▁input ▁imped ances ▁of ▁the ▁metal ▁and ▁slot ▁radi ating ▁pieces , ▁and ▁ ▁is ▁the ▁intr insic ▁imped ance ▁of ▁the ▁media ▁in ▁which ▁the ▁structure ▁is ▁imm ers ed . ▁In ▁addition , ▁Z sl ot ▁is ▁not ▁only ▁the ▁imped ance ▁of ▁the ▁slot , ▁but ▁can ▁be ▁viewed ▁as ▁the ▁complement ary ▁structure ▁imped ance ▁( a ▁di pole ▁or ▁loop ▁in ▁many ▁cases ). ▁In ▁addition , ▁Z met al ▁is ▁often ▁referred ▁to ▁as ▁Z screen ▁were ▁the ▁screen ▁comes ▁from ▁the ▁optical ▁definition . ▁The ▁thin ▁sheet ▁or ▁screen ▁does ▁not ▁have ▁to ▁be ▁metal , ▁but ▁rather ▁any ▁material ▁that ▁supports ▁a ▁ ▁( current ▁density ▁vector ) ▁leading ▁to ▁a ▁magnetic ▁potential ▁. ▁One ▁issue ▁with ▁this ▁equation , ▁is ▁that ▁the ▁screen ▁must ▁be ▁relatively ▁thin ▁to ▁the ▁given ▁w avel ength ▁( or ▁range ▁there of ). ▁If ▁it ▁is ▁not , ▁modes ▁can ▁begin ▁to ▁form ▁or ▁fr ing ing ▁fields