Figure shows the circuit of a flashing lamp, used at construction sites. The fluorescent lamp L, having negligible capacitance, is connected in parallel across the capacitor C of an RC circuit . There is a current through the lamp only when the potential difference across it reaches the breakdown voltage `V_L)`. In this event, the capacitor discharges completley through the lamp and lamp flashes momentarily.

Consider an instant, when the capacitor has just discharged through the flash light. Taking this instant as t=0, the time after which the lamp flashes momentarily is given by