The velocity of light is maximum in vacuum, which corresponds to option [B]. In vacuum, light travels at its maximum speed, approximately 299,792,458 meters per second (or about 186,282 miles per second) in a vacuum. This speed is often denoted as “c” in physics and represents the ultimate speed limit for anything with mass according to Einstein’s theory of relativity. Light slows down when it passes through other mediums such as air, water, or glass due to interactions with atoms and molecules, which temporarily absorb and re-emit photons. In denser materials like diamond or glass, the speed of light is significantly lower compared to its speed in vacuum. Understanding how light behaves in different mediums is crucial for applications ranging from optics and telecommunications to materials science and astronomy, where the properties of light interacting with various substances provide insights into their composition and behavior.