The correct option is D 32V/m
Accordingtoquestion:r=0.5mq=1.4×10−9CNow,findelectrifieldintensity:θ=arcradius⇒dl=Rdθ−−−−−(i)let,cheofdensity=pcheofthiselements=dq⇒dq=Rdθ−−−−−−−−(ii)Now,Eletricfieldduetotheelementsatlater:dE(magnitude)=Kdq/R2dE=Kdq/R2cosθi+Kdq/R2sinθ(−jdE=KdqR2[cosθi−sinθj]E=KpR[−2j]Now,wehaveP(chargeperunitlength)=θπRsothat,E=2KπR2(−j)E=2×9×109×1.4×10−9π×(0.5)2∴E=32V/msothecorrectoptionisD.