A hemispherical shell of radius a=1 cm has a surface charge density of m=4.00 uC/m^2.
I believe the surface area of a hemispherical shell is 2pi*r^2. 4.00 uC/m^2 is 4E10^-6 C/m^2 as well.
What is the magnitude of the electric field produced by the shell at the spherical center?