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

Short Solution (Best for NEET):

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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