Laser light goes from air, through a focusing lens and then back into air. In doing so it
A) speeds up twice.
B) slows down and then speeds up
C) slows down once.
D) slows down twice.

Question

Quizplus · Accepted Answer

When laser light passes from air through a focusing lens (typically made of glass or another transparent material) and then back into air, it slows down upon entering the lens due to the higher refractive index of the lens material compared to air. Upon exiting the lens and re-entering air, it speeds up again because it is moving from a medium of higher refractive index (the lens) to one of lower refractive index (air).

Laser Light Goes from Air, Through a Focusing Lens and Then