What is the relative dielectric constant for air?

The relative dielectric constant, also known as the relative permittivity, for air is effectively 1. This value indicates how much the electric field in air is reduced compared to that in a vacuum. Since air has properties very close to those of a vacuum, the dielectric constant remains close to unity.

In the context of this question, the other values presented (0.5, 2.5, and 3.0) do not accurately represent the dielectric constant of air. A dielectric constant less than 1, such as 0.5, is not physically meaningful as it cannot indicate a medium that has less capacitance than vacuum. Values greater than 1, like 2.5 and 3.0, typically correspond to solid and liquid materials that have significant polarizable components, which is not the case with air. Air can be treated as a vacuum for many practical purposes in telecommunications and radio frequency applications, supporting the assertion that its relative dielectric constant is approximately 1.