Which statement accurately compares the speed of light?

• A. The speed of light in glass is faster than in a vacuum.
• B. The speed of light in vacuum is less than 3 x 10^8 m/s.
• C. The speed of light in glass is slower than the speed of light in vacuum.
• D. The speed of light is constant in any medium.

Answer: (C)

The statement that the speed of light in glass is slower than the speed of light in vacuum is accurate because the speed of light varies depending on the medium it is traveling through. In a vacuum, light travels at its maximum speed, which is approximately 3 x 10^8 meters per second. However, when light passes through materials like glass, it interacts with the atoms in the glass, which causes it to slow down. This reduction in speed is represented by the concept of refractive index; glass has a higher refractive index than vacuum, resulting in light traveling slower in glass.

Understanding light's behavior in different mediums is crucial for applications in optics, such as in lenses and fiber optics, where the manipulation of light speed is essential for focusing and transmitting light efficiently. The distinction in speed helps explain a variety of optical phenomena, such as refraction and the bending of light when it enters a different material.