Question

Please, i did it, just want to be sure! A non-conducting sphere of radius R = 7 cm carries a charge Q = 4 mC distributed uniformly throughout its volume. At what distance, measured from the center of the sphere does the electric field reach a value equal to half its maximum value?

Answer 1

at 3.5cm from the center of the sphere.

Answer 2

The field is maximum at surface. And it decreases as we move inside the sphere as well as when we move outside the sphere.

You see that field is max at R, radius. As said above one point where field will be half would be at R/2 as field decreases uniformly as we move inside. The other distance would be
R√2 which lies outside the sphere.