Calculate the reactance XC by selecting a preferred value of the capacitor C and the frequency f. Capacitive reactance (symbol XC) may be defined as a measure of a capacitor's opposition to AC (alternating current). Quite similar to resistance, and therefore it is also measured in ohms. Howveer reactance can be a tad more complex compared to actual resistance.
It is because its value varies as per the induced frequency (f) of the input signal passing through the capacitor and also on the capacitance, C.
Capacitive reactance, XC = 1 / (2 × π × f × C)
where: XC = reactance in ohms (ohm), f = frequency in hertz (Hz), C = capacitance in farads (F)
The reactance XC will be larger at lower frequencies, and will get smaller with rising frequencies.
For constant DC signals which may be assumed as zero frequency, XC may be infinite (infinite opposition), which implies that capacitors will pass AC but tend to block DC.
Suppose a 1 µF capacitor has a reactance of 3.2 kΩ for a 50 Hz signal, but when the frequency gets on the higher range, may be at 10 kHz its reactance is measured at only 16 Ω.