Light travels in the form of electromagnetic waves. Electromagnetic waves are composed of oscillating electric and magnetic fields that propagate through space. These waves do not require a medium like air, water, or any other substance to travel through. This means that light can travel through a vacuum, such as outer space, as well as through various mediums like air, water, glass, or other transparent materials.
The speed at which light travels in a vacuum is approximately 299,792 kilometers per second (or about 186,282 miles per second) and is commonly denoted as the speed of light (c). When light encounters a different medium, such as air or water, its speed may change due to interactions with the atoms or molecules in that medium. This change in speed leads to effects such as refraction, where light bends as it passes through different materials.
It is important to note that while light can travel through various substances, it can also be absorbed or scattered by certain materials or objects, which may affect its propagation or visibility.