Invisibility of flint glass rod in carbon disulfide

[Amith2006]

# A rod of flint glass when immersed in carbon disulfide becomes almost invisible. It is said that it is because both have same refractive index. What I don’t understand is just because they both have same refractive index, why does it become invisible?

 

[Hootenanny]

How can you see a glass block submerged in water? What effects do you observe?

 

[Andrew Mason]

# A rod of flint glass when immersed in carbon disulfide becomes almost invisible. It is said that it is because both have same refractive index. What I don’t understand is just because they both have same refractive index, why does it become invisible?

Is there any reflection at the glass surface if both substances have the same index of refraction? If it is otherwise transparent, how would you detect the presence of the glass using only light?

AM

 

[Doc Al]

To appreciate how reflection and transmission occur at the boundary between two media requires an understanding of the Fresnel equations which are derived from Maxwell's equations for electromagnetic fields. It turns out that the reflection and transmission coefficients depend on the difference in refractive index of the two media*: the bigger the difference, the greater the reflection. With matching indices, the reflection is zero... everything gets transmitted, just like there was no boundary at all.

*They also depend on the angle of incidence and the polarization. For a start, go here: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/freseq.html#c1