code: public void setReflection(double reflection)
      {
          if(reflection <=0 || Double.isNaN(reflection) || Double.isInfinite(reflection) )
              throw new ArithmeticException("Reflection constant must be > 0, not " + reflection);
          this.reflection = reflection;
      }
docs: Sets the reflection constant, which must be greater than 0
  @param reflection the reflection constant