In which of the following media is the speed of light the greatest?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Vacuum
Light travels fastest in a vacuum, at about 3 × 108 m/s. In any material medium it slows down: a medium that slows it more is called optically denser, and glass, water and oil all have a refractive index greater than 1.