How does light change speed from glass to air?

In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.

In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.

In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.

In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.

In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.