What term describes materials that light cannot pass through?

The term that describes materials that light cannot pass through is opaque. Opaque materials block all light from passing through, meaning that they do not allow any light to be transmitted. This results in a solid appearance where objects behind the material cannot be seen at all. Examples of opaque materials include wood, metal, and stone.

In contrast, transparent materials, such as clear glass or water, allow light to pass through without significant obstruction, enabling clear visibility of objects on the other side. Translucent materials, like frosted glass, permit some light to pass through but scatter it in such a way that objects behind them cannot be clearly viewed. Reflective materials, such as mirrors, do not allow light to pass through; instead, they reflect it. However, their primary function is reflection, not blocking light entirely, as opaque materials do.