In this ckt. impedence is equal to (R-jXc) where Xc=1/wc. w=is the supply frequency.

Take the AC circuit to have a frequency = f.





Take the value of the capacitor to be = C.





Now, Impedance due to the Capacitor is Xc = 1 / (2 pi x f x C)





Pi is 22 / 7 2 pi f is Omega. So Impedance can also be written as (Omega x C)^-1.





Once you calculate the Impedance due to the Capacitor in Ohms, then add the resistance of the resistance R to it, and you get the total impedance in the circuit.





Impedance = (1 / 2 pi f C) + ( R) Ohms.

Z=R-j/(w C)

This is dependent on the frequency of the input voltage, as impedance is the vector sum of resistance and reactance.