#!/usr/bin/env python3

"""
Plot the scattering efficiency for 4 micron glass spheres.

This graph shows scattering as a function of wavelength.
"""

import numpy as np
import matplotlib.pyplot as plt
import miepython as mie

radius = 2  # in microns
lambda0 = np.linspace(0.5, 0.51, 2000)  # also in microns

# from https://refractiveindex.info/?shelf=glass&book=BK7&page=SCHOTT
m2 = 1 + 1.03961212 / (1 - 0.00600069867 / lambda0**2)
m2 += 0.231792344 / (1 - 0.0200179144 / lambda0**2)
m2 += 1.01046945 / (1 - 103.560653 / lambda0**2)
m = np.sqrt(m2)

plt.figure(figsize=(8, 4.5))

qext, qsca, qback, g = mie.efficiencies(m, radius * 2, lambda0)
plt.plot(lambda0 * 1000, qsca)

plt.title("BK7 glass spheres, 4 micron diameter")
plt.xlabel("Wavelength    [nm]")
plt.ylabel("Scattering Efficiency $Q_{sca}$    [—]")
# plt.savefig("02.svg", format="svg")
# plt.show()