There are various materials that can be opaque to visible light while being transparent to infrared light. One common example is glass. Ordinary glass, such as the one used in windows, is transparent to visible light and allows it to pass through. However, it can be opaque to certain wavelengths of infrared light.
This property is due to the fact that glass is made up of different chemical compounds, and its transparency or opacity depends on the specific composition. In some cases, glass can contain additives or impurities that absorb or reflect certain wavelengths of infrared light, making it opaque to those particular wavelengths.
Another example is certain types of plastics. Some plastics can be designed or formulated to be opaque to visible light while allowing infrared light to pass through. These plastics are often used in applications such as infrared windows, where they provide thermal insulation while still allowing the transmission of infrared radiation.
It's important to note that the transparency or opacity of a material to different wavelengths of light depends on its molecular structure and the energy levels of its atoms or molecules. By manipulating the composition and structure of materials, scientists and engineers can develop substances that exhibit specific optical properties, including being opaque to visible light and transparent to infrared light.