Explain the value of refractive index of water?

AI Thread Summary
The refractive index of water is commonly cited as 1.33, which differs from the calculated value of 9 due to the use of an incorrect relative permittivity for visible wavelengths. The relative permittivity of water varies with frequency, impacting the refractive index. The discussion emphasizes the importance of using appropriate values for specific wavelengths when calculating refractive indices. Understanding these nuances is crucial for accurate optical measurements. The conversation concludes with acknowledgment of the clarification provided.
Yen Pham
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I have studied about the formula of refractive index which is:
dbff99e30f01687f56047d647d3186d6.png
. That means in the case of water which have μ =1 (approximate) and ε = 81, then n should be 9. But why we often use the value n = 1.33 for water ?
Who can explain for me? I don't think the above formula is wrong, of course!
 
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You have taken a value for the relative permittivity which is not valid for visible wavelengths. The permittivity (and hence refractive index) changes with the frequency.
 
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Orodruin said:
You have taken a value for the relative permittivity which is not valid for visible wavelengths. The permittivity (and hence refractive index) changes with the frequency.
yeah, I got it! Thank you so much^^
 

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