Yes, there are certain mediums where light cannot propagate or travel. These are called opaque or non-transparent materials. Opaque materials absorb or scatter light, preventing it from passing through. When light encounters an opaque material, it is either absorbed by the material's atoms or molecules, or it interacts with the material's structure in a way that causes scattering.
Examples of opaque materials include metals like aluminum or copper, wood, stone, and thick layers of certain liquids or gases. In these materials, the atoms or molecules do not allow light to pass through them, resulting in the absorption or scattering of light.
It's important to note that even in materials that are generally considered transparent, there can be certain wavelengths or frequencies of light that are absorbed more readily, resulting in reduced transparency or even opacity in specific ranges. For example, certain gases are transparent in the visible light range but become opaque in the infrared or ultraviolet regions.
In summary, while light can propagate through many transparent materials, there are indeed mediums, such as opaque materials, where light cannot travel due to absorption or scattering.