The refractive indices of two media are denoted by n1 and n2, and the velocities of light in these two media are respectively v1 and v 2. If nz/ni is 1.5, which one of the following statements is correct?

The refractive index (n) of a medium is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in that specific medium (v), expressed as n = c/v [1]. This establishes an inverse relationship between the refractive index and the velocity of light in the medium [1]. For two media with refractive indices n1 and n2 and velocities v1 and v2, the relationship is n1 = c/v1 and n2 = c/v2. Dividing these equations gives the ratio n2/n1 = v1/v2 [2]. Given that n2/n1 = 1.5, it follows that v1/v2 = 1.5. Rearranging this equation results in v1 = 1.5 × v2. Therefore, the velocity of light in the first medium is 1.5 times the velocity of light in the second medium.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > What you have learnt > p. 159