We will not be able to see the small glass in the glass, the majority because the refraction index of vegetable oil to a glass with very similar values, so it is of the same type.
We will not be able to see a small glass in glass cases. Because the index of refraction of the glass of vegetable oil is very similar, making it as the same species.
We can not see the small glass in the big cup. Because the refractive index of the light of vegetable oil with glass is very similar and is of the same kind as .