Find Speed of Light in Medium with Index of Refraction

AI Thread Summary
To find the speed of light in a medium using the index of refraction, the formula n = c/v is applied, where n is the index, c is the speed of light in a vacuum (approximately 300,000 km/s), and v is the speed of light in the medium. For ethanol with an index of refraction of n = 1.36, the speed of light can be calculated by rearranging the formula to v = c/n. This results in v = 300,000 km/s / 1.36, yielding the speed of light in ethanol. Understanding that the index of refraction in a vacuum is 1.0 helps clarify that the speed of light in a vacuum is the standard reference point for these calculations. The key is to substitute known values into the equation to solve for the unknown speed in the medium.
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I am having a little bit of trouble finding the speed of light in a given medium when you are only supplied with the index of refraction. For example, I was given that n=1.36 in ethanol, and I had to find the speed of sound in ethanol. I know the equation for the index of refraction is n=c/v, but I am having problems with actually using it. For example, when only given that the index in a vacuum is 1.0, how do you know the speed, or do you use 300,000 km/s? Just a little bit confused here.
 
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the index of refraction = speed of light in vaccuum/speed of light in the medium.

put in the knowns. solve for the unknowns.
 
oooo said:
. For example, when only given that the index in a vacuum is 1.0, how do you know the speed, or do you use 300,000 km/s? .

you already know the answer.
 

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