A spherical shell of radius R is carries a uniform surface charge q. Take the reference point at ∞

What is the electric field at r>R? Here i is the unit vector in radial direction.

q/4πεo(r2 - R2 )  i q/4πεo(r2 + R2 )  i q/4πεor2  i qR/4πεor2  i

q/4πεor2  i

For r > R, it is assumed that the entire charge is concentrated at the center of the sphere. Thus, the effective distance of separation becomes = r.