If speed of light in air is 3 x 10^8s m/s, the speed of light in glass (with refractive index 1.5) would be

The speed of light in a medium is determined by its refractive index, which is defined as the ratio of the speed of light in a vacuum (or air) to the speed of light in that specific medium [1]. The formula is expressed as n = c / v, where 'n' is the refractive index, 'c' is the speed of light in air/vacuum, and 'v' is the speed in the medium. Given that the speed of light in air (c) is 3 x 10^8 m/s and the refractive index of glass (n) is 1.5, we can rearrange the formula to v = c / n. Substituting the values, v = (3 x 10^8 m/s) / 1.5, which equals 2 x 10^8 m/s [2]. This indicates that light travels slower in glass than in air due to the higher optical density of glass [3].

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 > QUESTIONS > p. 150
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 147