Question

How is the refractive index of a medium related to the speed of light?
A. Refractive index of a medium =$\dfrac{{Speed\,of\,light\,in\,medium}}{{Speed\,of\,light\,in\,vacuum}}$
B. Refractive index of a medium = $\dfrac{{Speed\,of\,light\,in\,vacuum}}{{Speed\,of\,light\,in\,medium}}$
C. Refractive index of a medium = $\dfrac{{Speed\,of\,light\,in\,air}}{{Speed\,of\,light\,in\,medium}}$
D. All

Answer 1

Hint: Refractive Index is the ratio of the speed of light in a vacuum to that in a second medium of greater density. In the case of Quartz glass, quartz glass is an amorphous solid having short range order of constituents.

Complete step by step answer:
Refractive Index is the value calculated from the ratio of the speed of light in a vacuum to that in a second medium of greater density.
In case of solids:
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 one which have the same physical properties such as electrical conductivity, thermal conductivity, mechanical strength, refractive index, in all the directions in space. This property is called isotropy.
Anisotropy – Anisotropic substances are one which have physical properties such as electrical conductivity, thermal conductivity, mechanical strength, refractive index, and are different in space. This property is called anisotropy.
An isotropic solid will have the same refractive index in all the directions. Hence, amorphous solids are isotropic in nature.
Refractive index is also given as velocity of light of a given wavelength in empty space divided by its velocity in any other substance.

So, the correct answer is “Option B”.

Note:
If the refractive index is lower for a medium then the velocity of light in that medium will be faster. Conversely, if the refractive index is higher than the speed of light will be slower. The value of the refractive index is always greater than one.
An isotropic solid will have the same refractive index in all the directions. Hence, amorphous solids are isotropic in nature.