The speed of the wave is: [tex]v = \lambda \cdot \nu[/tex]
a) If we are considering a light ray, speed is "c". The wavelenght will be:
[tex]\lambda = \frac{c}{\nu} = \frac{3\cdot 10^8\ m\cdot s^{-1}}{8.6\cdot 10^{13}\ s^{-1}}\cdot \frac{10^9\ nm}{1\ m} = \bf 3.49\cdot 10^3\ nm[/tex]
b) The frequency will be:
[tex]\nu = \frac{c}{\lambda} = \frac{3\cdot 10^8\ m\cdot s^{-1}}{566\cdot 10^9\ m} = \bf 5.3\cdot 10^{14}\ Hz[/tex]
