In 1870, the British physicist John Tyndall used sunlight and a stream of water to demonstrate how light _____.

John Tyndall's demonstration in 1870 using sunlight and a stream of water effectively illustrated the principle of total internal reflection, where light is guided along the water—akin to how it travels within optical fibers today. This experiment showcased that light can be channeled through a medium (in this case, water) and follow a specific path. This principle is foundational in fiber optics, as it allows light signals to be transmitted over distances with minimal loss. The demonstration was significant in understanding how light can be "contained" within a medium, leading to advancements in technologies that utilize light for communication and other applications.

While the other options—about light traveling through air, reflecting off surfaces, or being absorbed by solids—are valid properties of light, they do not specifically relate to the key insight of Tyndall's experiment regarding the directional channeling of light within a medium.