No, electromagnetic waves do not always travel at the same speed in media (non-vacuum) because their speed depends on the properties of the medium through which they propagate.
In a vacuum, electromagnetic waves, including visible light, radio waves, microwaves, X-rays, and gamma rays, all travel at the speed of light, denoted by the symbol "c." The speed of light in a vacuum is approximately 299,792,458 meters per second (or about 186,282 miles per second).
However, when electromagnetic waves pass through a medium such as air, water, glass, or any other material, their speed is generally slower than in a vacuum. This is because the interaction between the electromagnetic wave and the particles or atoms in the medium affects its propagation.
The speed of electromagnetic waves in a medium is determined by the medium's refractive index, which describes how much the speed of light is reduced when passing through that particular material. The refractive index is a property of the material and varies depending on factors such as its density and composition.
Different types of electromagnetic waves have different interactions with various materials. For example, visible light may travel at different speeds in different substances, leading to phenomena such as refraction or dispersion. This variation in speed is why we observe the bending of light when it passes through a prism or when it transitions from one medium to another.
In summary, the speed of electromagnetic waves in a medium (non-vacuum) is generally slower than the speed of light in a vacuum, and it can vary depending on the specific properties of the medium through which the waves are passing.