Thinking the small glass bead as a single point charge, the electric field generated by it is given by
[tex]E(r) = k_e \frac{Q}{r^2} [/tex]
where
[tex]k_e = 8.99 \cdot 10^9 N m^2 C^{-2} [/tex] is the Coulomb's constant
[tex]Q=8.0 nC=8.0 \cdot 10^{-9} C[/tex] is the charge of the bead
[tex]r=3.0 cm=0.03 m[/tex] is the distance at which we calculate the field.
Using these data, we find:
[tex]E=(8.99 \cdot 10^9 N m^2 C^{-2} ) \frac{(8.0 \cdot 10^{-9} C}{0.03 m)^2}=8.0 \cdot 10^4 N/C [/tex]
