According to Snell's law, what happens when light passes from a medium with a lower refractive index to a higher one?

When light transitions from a medium with a lower refractive index to one with a higher refractive index, it slows down and bends towards the normal line. This phenomenon is described by Snell's Law, which mathematically relates the angles of incidence and refraction to the refractive indices of the two media involved.

The normal line is an imaginary line perpendicular to the interface between the two media. As the light encounters the boundary, its speed decreases due to the increased density of the second medium. Consequently, the angle of refraction, which is measured from the normal line, becomes smaller than the angle of incidence, indicating that the light bends closer to the normal.

This behavior is crucial in understanding optical principles like focusing in lenses and the design of various optical devices. The tendency of light to bend towards the normal when entering a denser medium is foundational in optics and is a key point that helps predict how light behaves in different scenarios.