Final answer:
The electric field of a disk can be found using Gauss's Law by considering a Gaussian cylinder around a point on the disk's surface and solving for the electric field in terms of the surface charge density and permittivity of free space.
Step-by-step explanation:
To find the electric field of a disk with a given inner radius and outer radius, one must use Gauss's Law. Imagine an infinitesimal Gaussian cylinder with its ends parallel to the disk's surface. If the charge density is σ, the total charge inside this cylinder is σΔA. Since the electric field, E, is perpendicular to the surface outside the conductor and zero inside, the electric flux is EΔA through the outer face of the Gaussian surface. By Gauss's Law, which states that the electric flux equals the charge enclosed divided by the permittivity of free space, one can solve for E as E = σ/ε₀. This field is representative of the area just outside the surface of the disk.