Lake with wedge

Now imagining a huge lake, with a kind of wedge going through the earth, if the beach is on one of the edges of this wedge, how can we deal with the problem analogous to the first on the list, in this new situation?

In the case of light, this problem corresponds to the study of the prism.

• The following interactive application2 allows visualizing the total deviation of an incident ray, obtained by accumulating the partial deviations corresponding to the two refractions suffered; as for the graph shown, this deviation as a function of the angle of incidence clearly shows the existence of a minimum deviation, which corresponds to the position of the intermediate segment perpendicular to the bisector of the angle of the prism.

The following figure, taken from the previous interactive application, illustrates what happens with a ray of white light, composed of the juxtaposition of rays of various elementary colors (with different indices of refraction), when crossing the prism, causing the "separation" of these various colors3.

2 If you have Geogebra installed on your computer, you may prefer to import the applet from here and run it locally.
3 To clarify the color separation in the figure, slightly higher indices of refraction were considered.