Which one of the following statements is correct regarding the travel of a light beam from a rare to a dense medium?

When a light beam travels from an optically rarer medium (like air) to an optically denser medium (like glass or water), its speed decreases [2]. This reduction in speed occurs because the refractive index of a denser medium is higher, and the refractive index is defined as the ratio of the speed of light in a vacuum to its speed in the medium [5]. According to Snell's law, this change in speed causes the light ray to bend towards the normal at the interface of the two media [4]. Conversely, when light moves from a denser to a rarer medium, it speeds up and bends away from the normal [1]. Therefore, the correct observation for a rare-to-dense transition is that the light beam slows down and deflects toward the normal line [6].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 149
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
3. [5] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > What you have learnt > p. 159
4. [4] https://www.ncbi.nlm.nih.gov/books/NBK594230/
5. [6] https://www.khanacademy.org/science/in-in-class-12th-physics-india/in-in-ray-optics-and-optical-instruments/in-in-refraction-and-plane-surfaces/a/refraction-and-light-bending