### Task

When studying the reflection properties of such a material, it's convenient to analyze the spectrum of reflection coefficients. Their dependence on the wavelength $\lambda$ is due to the fact that the relative permittivity depends on the frequency $\omega$ of the incident light according to the microstructure of the material.

Most transparent materials in the optical range have the normal dispersion: their dielectric permittivity and refractive index increase with the light frequency $\omega$. It's a common practice to approximate this dependence with empirical formulas. An example of such an empirical formula is Cauchy's transmission equation:
$n(\lambda) = A + \frac{B}{\lambda^2},$
where $A$ and $B$ are some constants.

If we measure the ratio $R_p/R_s$ at the only one angle of incidence, it's impossible to obtain the refractive index $n$ unambiguously, because there are two different $n$ corresponding to the value of $R_p/R_s$. The graph below shows, how the value of $R_p/R_s$ depends on $n$ (measurements are made in air) with the angle of incidence $\Phi=60^\circ$.

In reflectometry.py on line 10-th you can choose the value of the angle of incidence $\Phi$ and plot a graph similar to the one above. You can use the cursor (values are displayed on the bottom left) to get data from it with the cursor.

There are two series of measurements $R_p/R_s$ versus $\lambda$ for fused glass $\rm SiO_2$ in air.

A1 With refractometry.py find the value of $n$ for each wavelength $\lambda$ in the table.

A2 Plot a linear graph $n(\lambda)$ and find the values of $A$ and $B$ for fused glass.