The density or thickness of a medium, such as air, does affect the speed at which waves propagate through it. This phenomenon is described by the concept of the wave's phase velocity. In general, the denser the medium, the slower the wave will travel through it.
In the case of light waves, which are electromagnetic waves, the speed of light in a vacuum is approximately 299,792 kilometers per second (or about 186,282 miles per second). However, when light passes through a medium, such as air, water, or glass, its speed is reduced. The reduction in speed is determined by the refractive index of the medium, which is a measure of how much the medium slows down the light. Generally, denser media have higher refractive indices, resulting in a slower speed of light propagation.
Similarly, for sound waves or sonar, the speed of sound is affected by the density of the medium through which it travels. In general, sound travels faster in denser media. For example, sound travels faster in water than in air because water is denser than air. The speed of sound also depends on other factors, such as temperature and humidity, but density is a significant contributor.
In summary, the density or thickness of a medium affects the speed of wave propagation. In most cases, denser media result in slower wave speeds, while less dense media allow for faster wave propagation.