The correct answer is option 2: LED converts electrical energy into light energy.

An LED is a device that emits light when an electric current passes through it. It is made up of a semiconductor material that emits photons (light particles) when energized by an electric current.

Option 1, "light energy into electrical energy," is incorrect because an LED does not generate electrical energy from light energy. It requires an external power source to operate.

Option 3, "thermal energy into light energy," is also incorrect as an LED does not convert heat energy into light energy. LED technology is known for its energy efficiency because it produces little to no heat compared to traditional light sources.

Option 4, "mechanical energy into electrical energy," is unrelated to the operation of an LED. LEDs do not generate electrical energy from mechanical energy, and they do not require any mechanical process to produce light.

In summary, an LED operates by converting electrical energy into light energy, which is emitted as visible light.