When a light ray enters into glass medium from water at an angle of incidence 0º, what would be the angle of refraction?

When a light ray enters a medium at an angle of incidence of 0º, it is striking the boundary along the normal line [1]. According to Snell's Law, the relationship between the angle of incidence (i) and the angle of refraction (r) is given by n1 sin(i) = n2 sin(r) [1]. If the angle of incidence is 0º, then sin(0º) = 0. Substituting this into the equation results in 0 = n2 sin(r), which implies that sin(r) must also be 0, making the angle of refraction 0º. In this specific case of normal incidence, the light ray does not bend and passes straight through the interface between water and glass without changing its direction. Therefore, the angle of refraction is 0º.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 148