How does the path of a light ray change when it moves from a less-dense into a more-dense medium? What do we call the ratio of the speed of light in a denser medium to its speed in a vacuum?

When a light ray strikes the surface of a denser medium, some is reflected and some is refracted. What can we say about whether energy is conserved in this situation?

1 Answer
Jan 16, 2018


The path of a light ray when it moves into a denser medium is that it is a straight line at an angle closer to the normal than the incident light (light in the original less-dense medium).


The degree to which the speed of light is altered from that in a vacuum is called the 'refractive index' of the material. The refractive index of a vacuum is 1.0000. All other refractive indices are higher.

The total light energy is conserved (stays the same). The energy in the reflected ray plus the energy in the refracted ray will equal the energy of the incident ray.