If the ray originated at B, it would follow the line AB to reach point A.
Ray is the incident ray.
Ray is the reflected ray.
Ray is refracted into the lucite.
Ray is internally reflected in the lucite.
Ray is refracted as it enters the air from the lucite.
Light may refract into a material where its speed is lower.
The angle of refraction is less than the angle of incidence.
The ray bends toward the normal.
Light may refract into a material where its speed is higher.
The angle of refraction is greater than the angle of incidence.
The ray bends away from the normal.
The light enters from the left.
The light may encounter an electron.
The electron may absorb the light, oscillate, and reradiate the light.
The absorption and radiation cause the average speed of the light moving through the material to decrease.
The speed of light in any material is less than its speed in vacuum.
The index of refraction, n, of a medium can be defined as
For a vacuum, n = 1
We assume n = 1 for air also
For other media, n > 1
n is a dimensionless number greater than unity.
n is not necessarily an integer.
Some Indices of Refraction
As light travels from one medium to another, its frequency does not change.
Both the wave speed and the wavelength do change.
The wavefronts do not pile up, nor are they created or destroyed at the boundary, so ƒ must stay the same.
The frequency stays the same as the wave travels from one medium to the other.
v = ƒλ
ƒ1 = ƒ2 but v1 v2 so λ1 λ2