Question

Which of the following is true about the value of the refractive index of quartz glass?
A) Same in all directions
B) Different in different directions
C) Cannot be measured
D) Always zero

Answer 1

Refractive Index of a material is the ratio of the speed of light in a vacuum to that in a second medium of greater density. Quartz glass is an amorphous solid. Quartz glass being an amorphous solid has short range order of constituents.

Complete solution:
Refractive Index of material is calculated by dividing the speed of light in vacuum to the speed of light in some other medium of greater density.
Solids are classified into two types:
A) Crystalline, they are also known as true solids
B) Amorphous solids

Crystalline and amorphous solids are distinguished based on their isotropy and anisotropy.
Isotropy – Isotropic substances are substances which have similar physical properties such as thermal conductivity, mechanical strength, electrical conductivity, refractive index, in all the directions in the space. These properties are called isotropic properties.

Anisotropy – Anisotropic substances are substances which have physical properties such as electrical conductivity, thermal conductivity, mechanical strength, refractive index, in different directions in space. These properties are known as anisotropic properties.
An isotropic solid will have the same refractive index in all the directions. Hence, amorphous solids are isotropic in nature.

Therefore, the A is the correct option.

Note: Remember that amorphous substances have the same refractive index in all directions. Amorphous solids are isotropic in nature. Refractive index has many applications. It is mostly applied to identify whether a particular substance, confirm its purity, or measure its concentration. It is also used to calculate the concentration of a solute in an aqueous solution.