Answer
$f=5.405\times 10^{14}Hz$
Work Step by Step
A formula relating the velocity, frequency, and wavelength of a wave is $$v=f\lambda$$ Solving for $f$ yields $$f=\frac{v}{\lambda}$$ Substituting values of $c=3.00\times 10^8m/s$ and $\lambda=555nm$ yields $$f=\frac{3.00\times10^8m/s}{555\times 10^{-9}m}=5.405\times 10^{14}Hz$$
