Now
[tex]\\ \rm\rightarrowtail \nu=\dfrac{1}{T}[/tex]
[tex]\\ \rm\rightarrowtail \nu=\dfrac{1}{8\times 10^{-5}}[/tex]
[tex]\\ \rm\rightarrowtail \nu=0.125(10^5)[/tex]
[tex]\\ \rm\rightarrowtail \nu=12500s^{-1}[/tex]
[tex]\\ \rm\rightarrowtail \nu=12500Hz[/tex]