move everything to src directory

1 files changed, 33 insertions, 0 deletions

diff --git a/src/optics.c b/src/optics.c
new file mode 100644
index 0000000..23e043d
--- /dev/null
+++ b/src/optics.c
@@ -0,0 +1,33 @@
+#include <math.h>
+#include "optics.h"
+
+/* From Table 4 in the paper. */
+static double A0 = 0.243905091;
+static double A1 = 9.53518094e-3;
+static double A2 = -3.64358110e-3;
+static double A3 = 2.65666426e-4;
+static double A4 = 1.59189325e-3;
+static double A5 = 2.45733798e-3;
+static double A6 = 0.897478251;
+static double A7 = -1.63066183e-2;
+static double UV = 0.2292020;
+static double IR = 5.432937;
+
+double get_index(double p, double wavelength, double T)
+{
+    /* Returns the index of refraction of pure water for a given density,
+     * wavelength, and temperature. The density should be in units of g/cm^3,
+     * the wavelength in nm, and the temperature in Celsius.
+     *
+     * See "Refractive Index of Water and Steam as a function of Wavelength,
+     * Temperature, and Density" by Schiebener et al. 1990. */
+    /* normalize the temperature and pressure */
+    wavelength = wavelength/589.0;
+    T = (T+273.15)/273.15;
+
+    /* first we compute the right hand side of Equation 7 */
+    double c = A0 + A1*p + A2*T + A3*pow(wavelength,2)*T + A4/pow(wavelength,2) + A5/(pow(wavelength,2)-pow(UV,2)) + A6/(pow(wavelength,2)-pow(IR,2)) + A7*pow(p,2);
+    c *= p;
+
+    return sqrt((2*c+1)/(1-c));
+}