The packing effciencyof the two dimensional cell square unit as showni

1.	The packing effciencyof the two dimensional cell square unit as shownis
Answer» 0.3927 0.6802 0.7405 0.7854 Solution :Package EFFICIENCY = `("AREA COVERED by particle")/("Total area")`If a is the LENGTH of unit cell, Area of unit all=`a^(2)` `"Face diagonal " AC=sqrt2a` `"But" "" AC = 4r` `therefore""sqrt2a =4r` `or""a = 2sqrt2r` `"No. of""""PARTICLES" = 4times1/4+1=2` `"Area occupied by particles" = 2timespir^(2)` `"Packing efficiency" = (2timespir^(2))/((2sqrt2r)^(2))=pi/4=0.7857` =`78.57%`.

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