/**************************************************************
!*  Calculate angle of refraction for an incident ray using   *
!*  Snell's Law                                               *
!* ---------------------------------------------------------- *
!* SAMPLE RUN:                                                *
!*                                                            *
!* Give indices for incident and refracting medium: 1.0 1.5   *
!*                                                            *
!* What is the angle of incidence? 30                         *
!*                                                            *
!* Refracted angle = 19.471221                                *
!*                                                            *
!* ---------------------------------------------------------- *
!* Ref.: "Problem Solving with Fortran 90 By David R. Brooks, * 
!*        Springer-Verlag New York, 1997".                    *
!*                                                            *
!*                          C++ Release By J-P Moreau, Paris. *
*                                  (www.jpmoreau.fr)          *
!**************************************************************
! Explanations:
! ------------               \ i! 
!                    incident \ !
!                      beam    \!
!                   ---------------------------
!                               !*
!                               ! *  refracted
!                               !r *   beam
!
!
!               Snell's Law:  n sin(i) = n sin(r)
!                              i          r 
!                           -1
!               or   r = sin  [(n / n ) sin(i)]
!                                i   r
!
!-------------------------------------------------------------*/
#include <stdio.h>
#include <math.h>


void main() {

  double ni, nr;             //indices of refraction (dimensionless)
  double incident,refracted; //angles from perpendicular (deg)
  double DegToRad;           //required for trig functions

  const double pi = 3.1415926537;

  DegToRad = pi/180.0;

  printf("\n Give indices for incident and refracting medium: ");
  scanf("%lf %lf", &ni, &nr);

  printf("\n What is the angle of incidence? ");
  scanf("%lf", &incident);

// Convert refracted angle to degrees before displaying its value

  refracted = asin(ni/nr*sin(incident*DegToRad));

  printf("\n Refracted angle = %f\n\n", refracted/DegToRad);

}

// end of file refract.cpp