definitiongeometryopticsrefractionvisible-light
I've gotten pretty good with the math when it comes to rays/optics, but I'm still missing some of the vocabulary. When a question says "A light ray is incident on glass at $30^{\circ}$" does this mean this is the angle from the normal? Here's the context of the question I'm asking this about:
A sheet of glass has n$_{red}$=1.52 and $n_{violet}$=1.55. A narrow beam of white light is
incident on the glass at 30°. What is the angular spread of the light inside the glass?
"Is it possible for a medium (here calcite) to have two refractive indices?"
Yes. Birefringence refers to the property that the refractive index of a material depends upon the polarization or direction of light through the material.
In general, reflection and refraction happen when light passes from one medium to another. You can see this if you see your own reflection in a window. Now, as a light ray approaches the critical angle, not only does the refracted ray get closer to the surface, but the amount of light transmitted gets less and less. At the critical angle, the refracted ray would be along the surface, but the amount of light is zero.
The graph below shows how much light is reflected at various angles of incidence. The graph on the right shows your situation of a ray of light moving from a dense medium to a lighter medium (glass to air, for example). At the critical angle, 100% of light is reflected, leaving none to propagate along the surface.
Best Answer
It just means that the path of the light intersects the plane of the glass. The angle between this ray and the perpendicular or normal to the surface is the angle of incidence. The reflected ray corresponding to a given incident ray, is the ray that represents the light reflected by the surface.