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In what way does the speed of light differ in air compared to water?

  1. It travels faster in air

  2. It travels slower in air

  3. It travels the same in both

  4. It varies randomly

The correct answer is: It travels faster in air

The speed of light is faster in air than in water due to the differences in the refractive indices of these two mediums. The refractive index is a measure of how much the speed of light is reduced inside a medium compared to its speed in a vacuum. In air, the refractive index is close to 1 (approximately 1.0003), which means that light travels almost at its maximum speed, approximately 299,792 kilometers per second. In contrast, water has a higher refractive index (about 1.33), which indicates that light slows down when it enters water, traveling at approximately 225,000 kilometers per second. This difference in speed is why light is seen to travel faster in air than in water. Understanding this concept is fundamental in fields such as optics and physics, as it affects how light behaves when transitioning between different materials.