- #1

Liquidxlax

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## Homework Statement

The refractive index of an equilateral prism of dense barium crown glass varies with wavelength as given in the table

wavelength (nm)...n

656.3...1.635

486.1...1.646

making use of Cauchy's dispersion formula determine the minimum angle of deviation for sodium light with wavelength = 589.3 nm

## Homework Equations

A/2 = theta prime

nsin(theta prime) = sin((A + deviation)/2)

(weird D)/(deviation) = (nf - nc)/(nd-1)

## The Attempt at a Solution

**2sin^-1((1.635)sin(30)) - 60 = deviation = 49.7 degrees**

2sin^-1((1.646)sin(30)) - 60 = deviation = 50.8 degrees

weird D = 50.8 - 49.7 = 11.1 degrees

2sin^-1((1.646)sin(30)) - 60 = deviation = 50.8 degrees

weird D = 50.8 - 49.7 = 11.1 degrees

My problem is that I'm not sure how to find nd to finish the question.

i know i can use

**n of wavelength = A + B/(wavelength)^2 + C/(wavelength)^4**

but that doesn't leave me with an n between 1.635 and 1.646 and that is my problem