# Low pass filter transfer function

I am calculating the transfer function of a low pass RC filter and I have gotten $$\frac{1}{1+jωRC}$$ which is correct. But somehow it seems $$ωRC = \frac {ω}{ω_0}$$ that refers to the cutoff freqency which is set to 500Hz. Where does this $$ωRC = \frac {ω}{ω_0}$$ come from?

• simply defines $RC \triangleq \frac{1}{\omega_0}$. – robert bristow-johnson Mar 13 at 1:46