z = \frac{Δ λ}{λ_{0}} = \frac{λ - λ_{0}}{λ_{0}} = \frac{λ}{λ_{0}} - 1

${z = \frac{\Delta \lambda}{\lambda_0} = \frac{\lambda - \lambda_0}{\lambda_0} = \frac{\lambda}{\lambda_0} - 1}$

Error