Answer:
The brightness of the bulb will get increased.
Explanation:
There is an inverse relationship between capacitive reactance and frequency.
[tex]\chi _{c}\propto \frac{1}{f}[/tex]
In the given problem, an AC source is connected to a series combination of a light bulb and a variable capacitor. The frequency of A.C source increases in this case. The capacitive reactance will get decreased. The current will get increased then the brightness of the bulb will increase.
If the capacitance is increased, the bulb's brightness will increase.
