Question

Which of the following material has maximum optical density?
A. Glass
B. Water
C. Pearl
D. Diamond

Answer 1

HINT: Basically, the physical density would be the ratio of mass to the volume, and optical density measures the speed of light while passing through an optically dense medium.
The optical density is a property of a transparent material that measures the speed of light through the material. The extent to which any optically dense medium bends transmitted light rays towards or away from the normal is called optical density. The light passing via an optically dense medium towards the normal and the same light passing via any rarer medium such as air, it bends away from the normal.

Complete step by step answer:
Now, let us understand the phenomenon of optical density and its effect on the light passing via a medium by comparing the two media.
Consider two mediums: glass and air. When a beam of light passes from air to glass. The speed of the light decreases in the glass. Therefore, the light bends towards the normal. It tells us that the glass is optically denser than air which means the velocity of the light in glass is less than the velocity of it in rarer medium(air).
Glass: the refractive index of glass if 1.5 means that light will take 1.5x more unit of time to propagate a certain distance in glass than it takes in vacuum.
Water: the refractive index of water is 1.333.
Pearl: the refractive index of pearl is 1.52-1.69.
Diamond: the refractive index of diamond is 2.42, that is highest. The optical density is directly dependent on the refractive index. Thus, the diamond is the material that has maximum optical density.

So, diamonds have maximum optical density. The correct answer is option (D).

Note: 1. More the refractive index of a medium, more is its optical density,
2. Lesser is the refractive index of a medium, lesser is its optical density.
Example: air-optically less dense (refractive index is 1), Glass-optically more dense (refractive index is 1.5)