y > 3
E = σ/2ϵ j = 10-8/(2 × 6π × 8.854 × 10-12) j = 29.959 j
Magnitude of electric field at all points is same since the electric field due to an infinite plane (or) disc is uniform.
For y < 3
E = -29.959 j
For y<3, electric field is directed along negative y-axis. Unit vector along negative y-direction is –j.