For common materials like glass, the wavelength dependence of the refractive index at visual wavelengths is given approximately by  n(λ) = b + c/ λ² , where b and c are constants. The table below gives values of l and n for the crown glass of Example 30.4. Determine a quantity that, when you plot n against it, should give a straight line. Make your plot, establish a best-fit line, and use the line to determine the constants b and c.