Answer
$T=1.85\times 10^{-15}s$
Work Step by Step
A formula relating the frequency and period of a wave is the equation $$T=\frac{1}{f}$$ Replacing $f$ with the value of $f=5.405\times 10^{14}Hz$ yields $$T=\frac{1}{5.405\times 10^{14}Hz}=1.85\times 10^{-15}s$$
