Assertion (A) : Kerosene having higher refractive index is optically denser than water, although its mass density is less than that of water.
Reason (R): The speed of light decides whether a medium is optically rarer or optically denser. An optically denser medium may not possess greater mass density.
Answers
Answer:
(A) Both a and r correct and r is the correct explanation for a
The assertion and reason are true and the reason is the correct explanation of assertion.
The refractive index purely depends on the speed of light in the material and has nothing to do with the mass density of a material.
Mass density depends on the nature of a material and is an intensive property.
The optical density, also an intensive property, determines the refractive index of a material.
The material will have a lower refractive index if the speed of light in it is faster than any other material. A material with a lower refractive index will have a lower optical density but will have a higher speed of light when passing through it.
Kerosene is optically denser than water but it still has a lower mass density than water. This justifies that the two properties are not always related.