Assertion (A): The speed of light in an optically rarer medium is greater than that in an optically denser medium.
Reason (R): One light year equals to \(9.5 \times 10^{12}\), km.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
An optically rarer medium has a lower refractive index, meaning light travels faster in it, so A is true. A light-year is the distance light travels in one year, approximately \(9.46 \times 10^{12}\), km, so R is true. However, the definition of a light-year does not explain the speed of light in different media.
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: The mass density of an optically denser medium is greater than that of an optically rarer medium.
Reason R: Optical density is found by the ratio of the speed of light in two media while mass density is mass per unit volume.
In the light of the above statements, choose the correct answer from the option given below.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
View Answer
Mass density and optical density are not directly related. For example, oil is optically denser than water but has a lower mass density. Thus, Assertion A is false but Reason R is true.