▁a ▁way ▁that ▁provides ▁information ▁about ▁the ▁sample , ▁or ▁the ▁beam ▁itself . ▁From ▁the ▁previous ▁equation , ▁it ▁can ▁be ▁dedu ced ▁that ▁the ▁observed ▁image ▁depends ▁not ▁only ▁on ▁the ▁amplitude ▁of ▁beam , ▁but ▁also ▁on ▁the ▁phase ▁of ▁the ▁electrons , ▁although ▁phase ▁effects ▁may ▁often ▁be ▁ignored ▁at ▁lower ▁magn ifications . ▁High er ▁resolution ▁imag ing ▁requires ▁th inner ▁samples ▁and ▁higher ▁energ ies ▁of ▁incident ▁electrons , ▁which ▁means ▁that ▁the ▁sample ▁can ▁no ▁longer ▁be ▁considered ▁to ▁be ▁absor bing ▁electrons ▁( i . e ., ▁via ▁a ▁Be er ' s ▁law ▁effect ). ▁Instead , ▁the ▁sample ▁can ▁be ▁mode led ▁as ▁an ▁object ▁that ▁does ▁not ▁change ▁the ▁amplitude ▁of ▁the ▁incoming ▁electron ▁wave ▁function , ▁but ▁instead ▁mod ifies ▁the ▁phase ▁of ▁the ▁incoming ▁wave ; ▁in ▁this ▁model , ▁the ▁sample ▁is ▁known ▁as ▁a ▁pure ▁phase ▁object . ▁For ▁sufficiently ▁thin ▁spec im ens , ▁phase ▁effects ▁domin ate ▁the ▁image , ▁comp lic ating ▁analysis ▁of ▁the ▁observed ▁intens ities . ▁To ▁improve ▁the ▁contrast ▁in ▁the ▁image , ▁the ▁T EM ▁may ▁be ▁operated ▁at ▁a ▁slight ▁def ocus ▁to ▁enh ance ▁contrast , ▁ow ing ▁to ▁convolution ▁by ▁the ▁contrast ▁transfer ▁function ▁of ▁the ▁T EM , ▁which ▁would ▁normally ▁decrease ▁contrast ▁if ▁the ▁sample ▁was ▁not ▁a ▁weak ▁phase ▁object . ▁ ▁The ▁figure ▁on ▁the ▁right ▁shows ▁the ▁two ▁basic ▁operation ▁modes ▁of ▁T EM ▁– ▁imag ing ▁and ▁diff raction ▁modes .