The basic relationship between frequency and wavelength for light (which is an electromagnetic wave) is
[tex]c= f \lambda[/tex]
where c is the speed of light, f the frequency and [tex]\lambda[/tex] the wavelength of the wave.
Using [tex]\lambda=4.5 \cdot 10^{-7} m[/tex] and [tex]c=3 \cdot 10^8 m/s[/tex], we can find the value of the frequency:
[tex]f= \frac{c}{\lambda}= \frac{3 \cdot 10^8 m/s}{4.5 \cdot 10^{-7} m}=6.7 \cdot 10^{14} Hz [/tex]
