Final answer:
The electric field 5 m above an infinite uniform charged plane is constant in magnitude and direction, regardless of distance from the plane. For two planes with opposite charges, the field strength doubles between them while canceling outside.
Step-by-step explanation:
The electric field from an infinite charged plane is characterized by its constant magnitude and direction at any given distance from the plane, due to the symmetry and the infinite extent of the plane. In the scenario where you are 5 m above an infinite uniform charged plane, the electric field does not depend on your altitude because no matter how high you are, the plane still stretches to infinity and appears the same. According to Gauss's law, if you were above the plane, the electric field would point upwards in the direction away from the plane, and if you were below the plane, it would point downward towards the negative direction.
In the case of two infinite planes with equal but opposite charge densities, the electric field would be directed from the positively charged plane towards the negatively charged plane, and its magnitude would be twice that of a single plane's electric field in the region between the planes. This is because the electric fields from each plane add together in the region in between. Outside of the two planes, the fields cancel each other, resulting in a net electric field of zero outside the planes.