Final answer:
Light travels fastest in a vacuum at a speed of 3 × 10^8 m/s, and slows down when it passes through other materials such as water or glass. It can induce molecular vibrations and bends upon entering a different medium—a process known as refraction, which is not exclusive to solids.
Step-by-step explanation:
When discussing the interactions of light with various materials such as molecules, atoms, and ions, it's important to address some common misconceptions and establish the fundamental behaviors of light. One crucial fact is that light always travels faster in a vacuum compared to any other medium. The universally accepted speed of light in a vacuum is 3 × 108 m/s (denoted as 'c').
When light enters a medium such as glass or water, it slows down and its speed becomes less than 'c'. For instance, light travels through water at approximately three-fourths the speed of light in a vacuum. In diamond, it slows down to just 41 percent of 'c'. Moreover, light can indeed induce molecular vibrations, especially when absorbed by specific molecules that match the energy transition of the absorbed light.
This is a foundational concept in spectroscopy and is used to understand the structure and composition of substances. Furthermore, when light encounters the boundary between two different mediums, it refracts or bends, a process dependent on the speed of light in those respective mediums. The bending of light, or refraction, is more pronounced when there is a greater discrepancy between the speed of light in the two media.