Find out, from Table 10.3, the medium having highest optical density. Also find the medium with lowest optical density
We know that,
A substance having higher refractive index has higher optical density.
From table 10.3, we can infer that
Diamond has the highest refractive index (2.42)
Hence, it has the highest optical density.
Air has the lowest refractive index (1.0003)
Hence, it has the lowest optical density.