Compared with the speed of light in a vacuum, the speed of light in the empty space between molecules in glass is
A) more.
B) the same.
C) less.
D) none of the above.
The correct answer and explanation is:
The correct answer is C) less.
When light travels through a material, such as glass, its speed decreases compared to the speed of light in a vacuum. This is because the light interacts with the molecules of the medium. In a vacuum, light moves at its maximum speed, which is approximately 3 x 10^8 meters per second. This is the speed of light in a vacuum, often referred to as “c.”
However, when light passes through materials like glass, the electromagnetic waves interact with the atoms and molecules of the glass. This causes delays in the transmission of light. The light still moves at a very fast pace, but it is slower than in a vacuum due to these interactions. The factor by which light slows down in a medium is called the refractive index of the material. Glass has a refractive index typically between 1.5 and 1.7, which means light travels at 1/1.5 to 1/1.7 of its speed in a vacuum when passing through the glass.
The refractive index depends on the material and its optical properties. A higher refractive index indicates a greater reduction in speed. In glass, for instance, the light’s speed might be reduced to approximately 2 x 10^8 meters per second.
This reduction in speed occurs because of the constant absorption and re-emission of photons by the electrons in the material, which effectively slows down the propagation of the light wave. This process is more complicated than simply passing through empty space and results in the decrease of light’s speed in the medium.
Therefore, compared to its speed in a vacuum, the speed of light in the empty space between molecules in glass is slower.