Let's break down the steps to determine what happens to the speed of light as it moves from air into an empty glass bottle.
1. Identify the speeds of light in different media:
- [tex]\( \text{Speed of light in air} = 299,700,000 \, \text{m/s} \)[/tex]
- [tex]\( \text{Speed of light in glass} = 200,000,000 \, \text{m/s} \)[/tex]
2. Compare the speeds of light in air and glass:
- The speed of light in air is [tex]\( 299,700,000 \, \text{m/s} \)[/tex].
- The speed of light in glass is [tex]\( 200,000,000 \, \text{m/s} \)[/tex].
3. Determine the change in speed:
- Calculate the difference in speed as light moves from air to glass:
[tex]\[
\Delta \text{speed} = \text{Speed of light in air} - \text{Speed of light in glass}
\][/tex]
[tex]\[
\Delta \text{speed} = 299,700,000 \, \text{m/s} - 200,000,000 \, \text{m/s} = 99,700,000 \, \text{m/s}
\][/tex]
4. Interpret the change in speed:
- Since [tex]\(\Delta \text{speed} = 99,700,000 \, \text{m/s}\)[/tex] is a positive number, the speed of light decreases when it moves from air to glass.
Therefore, the speed of the light wave decreases when it moves from the air into the glass.
The answer to the question is:
A. It decreases.
