Question

The speed of light is 3.00 × 108 m/s in the vacuum of space. In a medium with what index of refraction would light travel slowest?

n = 1.00
n = 1.20
n = 1.50
n = 1.62

Answer 1

Index of refraction can be calculated using the following formula:

`n=(c)/(v)`

where
`c=3 * 10^8 (m)/(s)` in a vacuum and "n" is the index of refraction. So we must calculate our velocity by manipulating the index of refraction formula and isolate v and so:

`v=(c)/(n)`

We could go one by one and calculate the velocity or use logic. If you divide by a larger number the output will be a smaller number. Therefore, the answer would be n=1.62 is the slowest.

`v=(3 * 10^8 (m)/(s))/(1.62)= 1.85185 * 10^8 (m)/(s)`

By that logic when n=1 light would travel the fastest of these four scenarios. The key thing to understand about these problems is that the speed of light slows down as it goes through a medium, in a vacuum it's 3 x 10^ 8 m/s but as it goes through say air or water light slows down.