A body is executing simple harmonic motion with frequency $n$, the frequency of its potential energy is

Given,
frequency of $\mathrm{SHM}=n$
As we know time period is the time in which particle complete its one revolution.

Now we know that in one time period particle passes through mean position and extreme position two times.

So, In one time period $PE$ become maximum & minimum two times. It means frequency of $PE$ is $2n$.