Challenge #1a, Refractive index of Crownglass against wavelength

The refractive index of BK-7 crown glass is calculated using the Sellmeier equation:

$$ n(\lambda) = \sqrt{ 1 + \sum_{k=1}^{3} \frac{a_k \lambda^2}{\lambda^2 - b_k} } $$

where \(\lambda\) is the wavelength in nanometers, with constants:

This formula is used to compute the refractive index of BK-7 across the visible spectrum.