To understand what happens to the speed of light as it passes from air into glass, let's analyze the data provided in the table:
[tex]\[
\begin{tabular}{|c|c|c|c|c|}
\hline
& Water & Diamond & Glass & Air \\
\hline
\begin{tabular}{c}
Speed of \\
light $( m / s )$
\end{tabular}
& $225,000,000$ & $125,000,000$ & $200,000,000$ & $299,700,000$ \\
\hline
\end{tabular}
\][/tex]
1. Speed of Light in Air: According to the table, the speed of light in air is [tex]\(299,700,000 \text{ m/s}\)[/tex].
2. Speed of Light in Glass: According to the same table, the speed of light in glass is [tex]\(200,000,000 \text{ m/s}\)[/tex].
When light transitions from one medium to another, its speed changes. In this case, it goes from air (a medium with relatively low optical density) to glass (a medium with higher optical density).
3. Comparison:
- Speed of light in air: [tex]\(299,700,000 \text{ m/s}\)[/tex]
- Speed of light in glass: [tex]\(200,000,000 \text{ m/s}\)[/tex]
From this comparison, it's clear that the speed of light decreases as it moves from air to glass.
4. Conclusion:
- Since the speed of light in air is greater than the speed of light in glass, the correct answer is that the speed of light decreases when it passes from air into glass.
Therefore, the correct choice is:
- C. It decreases.
