# If a material has an index of refraction of 2.25, what is the speed of light through it?

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To solve, apply the formula of index of refraction which is:

`n=c/v`

where,

n - index of refraction

c - velocity of light in a vacuum ( 3 x 10^8 m/s) and

v - velocity of light in a medium

So, plug-in n=2.25 and c=3 x 10^8 to the formula.

`2.25=(3xx10^8)/v`

Then, multiply both sides by v.

`2.25*v=(3xx10^8)/v * v`

`2.25v=3xx10^8`

And, divide both sides by 2.25.

`(2.25v)/2.25=(3xx10^8)/2.25`

`v=1.33xx10^8` **Hence, the velocity of light in the medium is `1.33xx10^8` m/s.**