Refraction, the bending of light, happens when light moves between substances with different refractive indices. Light bends because its speed changes.
As light enters a denser medium (Medium 2), it slows down compared to Medium 1. The refracted light ray bends away from the normal, showing light's speed is slower in Medium 2 than in Medium 1. This bending is due to the difference in refractive indices.
In summary, light bends away from the normal because it slows down in the denser medium (Medium 2).