Glowing gherkin

Gherkin is producing light because it is an electrolyte. When we apply voltage, current start flow and stimulate ions inside gherkin to luminescence. (An electrolyte is a substance that ionizes when dissolved in suitable ionizing solvents such as water)

The gherkins are pickled and the salt in the pickling juice is responsible for the glow. Electrons in the sodium atoms get excited and when they fall back to their original levels, photons are released. These give a characteristic yellow/orange colour.