An AC voltage source of variable angular frequency ω and fixed amplitude V_o is connected in series with a capacitance C and an electric bulb of resistance R (inductance zero). When ω is increased then, 

The bulb glows brighter

Impedance is $ Z = \sqrt{R^2+ \frac{1}{\omega^2 C^2}}$

When frequency increases Z decreases.

$\Rightarrow I = \frac{V}{Z}$ Increases.

As more current flows through the circuit with increased frequency, the bulb glows brighter.