A negative charge does not directly affect the rate at which electromagnetic waves travel through space. The speed of electromagnetic waves in a vacuum, such as light, is determined by the properties of the medium, specifically the permittivity (ε₀) and permeability (μ₀) of free space. In vacuum, electromagnetic waves travel at the constant speed of light, denoted as 'c,' which is approximately 299,792,458 meters per second.
The presence of a negative charge, by itself, does not alter the speed of electromagnetic waves. However, it can interact with electromagnetic fields and influence their behavior in other ways. For example, a negative charge can generate its own electromagnetic field, which can interact with other electromagnetic fields and cause effects such as scattering or absorption of the waves.
In a medium other than vacuum, such as a material or a plasma, the presence of charges can have additional effects. The properties of the medium, including its permittivity and permeability, can be influenced by the presence of charges, affecting the speed at which electromagnetic waves propagate through that medium. This is often described by the refractive index of the material, which determines how light is slowed down or refracted as it passes through.
To summarize, while a negative charge itself does not directly affect the speed of electromagnetic waves in vacuum, it can interact with electromagnetic fields and have an impact on wave behavior. In other media, charges can influence the speed of electromagnetic waves through their interaction with the properties of the medium.