Translations:Sketcher ConstrainSnellsLaw/9/en

where:
 * is a sketch object
 * and are two integers identifying the endpoint of the line in medium with refractive index of n1.  is the line's index in the sketch (the value, returned by Sketch.addGeometry), and  should be 1 for start point and 2 for end point.
 * and are the indexes specifying the endpoint of the second line (in medium n2)
 * is the index specifying the line indicating the position of the interface between medium n1 and medium n2
 * is a floating-point number equal to the ratio of refractive indices n2/n1