$${v = \frac{\Delta \lambda}{\lambda_0} c = \frac{0,90\, \mathrm{nm}}{500,7\, \mathrm{nm}} 299\, 792\, 458\, \mathrm{m/s} \\ = \underline{\underline{5,39 \times 10^5\, \mathrm{m/s}}}}$$