Speed of Light and Light Year – Rankers Physics

Refraction by Plane Surfaces: Practice Problem & Solution

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.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Refraction by Plane Surfaces. Understanding the underlying formula is key to arriving at the correct answer below:

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.

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