Question

Refractive indices of aromatic molecules are higher than those of saturated hydrocarbons; for example, for benzene and cyclohexane, n= 1.50112 and 1.4290 at 20^o, respectively. (This is the reason why, when viewed in a clear beaker, benzene or toluene appears to partially disperse white light into a "rim" of colors.) Can you suggest a reason why n for C₆H₆ is greater than n for C₆H₁₂?

Answer 1

This is pretty simple

density of C6H6 --> 1 mol will occupy only certain volume, with a mass of 80

density of C6H12 --> 1 mol occupies a mas of 84

therefore

the refractive index shows:

n = c/v

c = speed of light in vaccum (constant) and v = the speed of light in that specific media

therefore, the higher the n, the slower the velocity of light

according to light velocity in medium, the higher density, the lower speed of light in the medium

this makes sense since C6H6 is higher in density, expected n must be higher.

Extension:

Essentially, the more refraction the substance is; the more it will "refract" or "deviate" the light passing thorugh it. For example, a very refractive substance will make light to travel more in order to reach a place.

This is viewed in the beaker example. You will see disperse and almost a "dirty look" in the substance that refract more the light.

Then; if the index is high, it means the speed of light in that medium is low. If the index is low, then expect a very high velocity in the medium

Summary: the more "n" index; the lower the velocity travel; therefore the more "funny" or "strange" look of the light it will have