What is the index of refraction of this substance?

[vucollegeguy]

The speed of light in a certain substance is 79.0% of its value in water.
What is the index of refraction of this substance?


Here's what I've done so far:

(3.0*10^8 m/s)(0.79) because its 79%.
In water, the n=1.003.

I'm not sure where to go from there.
Any help would be greatly appreciated!
Thanks in advance.

 

[Redbelly98]

The speed of light in a certain substance is 79.0% of its value in water.
What is the index of refraction of this substance? Here's what I've done so far:

(3.0*10^8 m/s)(0.79) because its 79%.
In water, the n=1.003.

No, that's n for air.
n for water is ____?
The speed of light in water is ____?

 

[vucollegeguy]

correction:
n=1.33
and the speed of light in water (3x10^8)/(1.33)=2.25x10^8

 

[Redbelly98]

That's right. And:

The speed of light in a certain substance is 79.0% of its value in water.

Hope that's enough.

 

[vucollegeguy]

Since 79%, mulitplying (2.26x10^8)(0.79)= 1.78x10^8.
Correct?

 

[Redbelly98]

Yes.