Calculating Refractive Index of Liquid Mixtures: Is There a General Formula?

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SUMMARY

There is no general formula for calculating the refractive index of liquid mixtures due to the variable composition throughout the mixture. However, a linear approximation can be used: n = (n1V1 + n2V2) / (V1 + V2), where n represents the refractive indices and V represents the volumes of the liquids involved. It is crucial to note that the refractive index is not directly related to density, contradicting some common assumptions. Accurate calculations require consideration of the mixture's uniformity and composition.

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Ogulnius
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Is there a general formula to calculate the refractive index of a mixture of two liquids of known refractive index, e.g. water and ethanol, or water and glycerol?
 
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No. That is because a mixture is not a constant composition - the composition varies throughout the mixture. The index will be different at all these points.
 
O unless you want averages, then i guess so. Its been a while since I've done physics, but I think the refractive index is dependent only on density, and you can calculate the average density.
 
Of course, it is assumed that the liquids are thoroughly mixed and that the mixture is of constant composition.

As a coarse approximation you can use a linear formula:
n={ n_1V_1+n_2V_2\over V_1 + V_2 }
where n hold for the refractive indexes and V for the volumes.
But this is just an approximation.

Refractive index is not related to density.
 

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