According to the Cauchy's equation,

mu = C + B/((lamda)2)
where C and B are constant and mu and lambda are the wave length and reflective index respectively.

Obtain the suitable least square approximation and �nd the given constant C and B using the following data.

My question is can we use the linear least square approximation since there is one independent variable(lambda) or should we use any other method?

The relation is linear, but in terms of 1/λ ... or is that 1/λ2 ?

So I'd use the linear least squares, but label the axes accordingly.